If you’ve ever collected baseball cards, comic books, stamps, or those limited edition commemorative plates, you understand the concept of the “Holy Grail” item. It’s that last, hard-to-find, incredibly rare, usually expensive piece that you must have before you can officially say your collection is “complete.” If you’re a collector of vintage home video game cartridges (or “carts”), sometimes that can mean paying a pretty penny for the pièce de résistance.

NINTENDO ENTERTAINMENT SYSTEM (NES)

Back in the day, everyone had a Nintendo. Due to the console’s popularity, there are a large number of collectors willing to pay the equivalent of a new car for some of the system’s very rare carts.

1. STADIUM EVENTS

Price Range: $2,600 - $41,300; $10,000 for the box alone

Why So Expensive? Stadium Events was released by Bandai in 1987 as one of the few games available in America that was made for the company’s Family Fun Fitness mat—a soft, plastic controller you walked, ran, and jumped on to make the game characters move. Nintendo bought the rights to the game and the mat in 1988 and re-released them as WorldClass Track Meet and the Power Pad controller. To avoid consumer confusion, Nintendo pulled all copies of Stadium Events from shelves and had them destroyed, but not before approximately 200 carts had already been sold. Of those 200, collectors believe that only about 20 complete copies of the game exist today, making them a real rarity.

Stadium Events made headlines in 2010 with two high-profile eBay sales: A North Carolina woman was cleaning out her garage and found an old Nintendo and a handful of games, including Stadium Events. She put them up on eBay without high expectations and was amazed to see the bids steadily climb up to $13,105. While the game itself is valuable, the winning bidder was most interested in the cardboard box in which it came; since most kids threw the box away after tearing open a new game, intact boxes for any title are really hard to come by, but especially so for Stadium Events. Empty Stadium Events boxes have been known to sell for $10,000 alone.

After hearing of the success of this eBay seller, a man in Kansas dug up a factory-sealed copy of the game that he was just about to donate to Goodwill. He had purchased the game in 1987, but could never find the fitness mat to go with it. It was still sealed because he’d meant to return it. His game became only the second known sealed copy in existence. When his eBay auction ended, the game sold for an amazing $41,300.

Earlier this year, another sealed copy of Stadium Events sold on eBay for $35,100, meaning the game has lost a little bit of its value, but not much.

The same game repackaged by Nintendo, World Class Track Meet, generally sells for about $5 on eBay.

2. 1990 NINTENDO WORLD CHAMPIONSHIPS (GRAY AND GOLD EDITIONS)

Price Range: Gray: $8,500 - $20,200; Gold: $26,677

Why So Expensive? In 1990, Nintendo held a 30-city gaming tournament to find the best player in the world. Players had to get the best score in demo versions of three games—Super Mario Bros., Rad Racer, and Tetris—all within a six-minute time limit.

At the end of each city’s tournament, the winners of each of three age groups were given special gray Championship cartridges exactly like those used in the competition, meaning only 90 of these cartridges were distributed. A gold version was sent out to those who won a promotional contest in the pages of Nintendo Power magazine. Only 26 gold games were produced, so they’re especially hard to find and command a higher price today; the last one to sell on eBay went for $26,677.

3. NINTENDO CAMPUS CHALLENGE

Price Range: $14,000 - $20,100

Why So Expensive? In the early 1990s, Nintendo held competitions on college campuses and at popular Spring Break destinations. Like the World Championships, players had six minutes to play for high scores in demo versions of three games: Super Mario Bros. 3, PinBot, and Dr. Mario.

Most copies of the game were destroyed after the competition tour ended, but one Nintendo employee kept his cart and sold it to Rob Walters at a garage sale in 2006. This garage sale is legendary among retrogamers, as Rob bought all kinds of NES Holy Grails for only $1,000. By the time he resold everything, he’d made 50 times that. Part of that $50,000 was the Campus Challenge cartridge, which went for $14,000. Shortly after, the buyer of the cart, collector J.J. Hendricks, turned around and sold it on eBay for $20,100. As far as anyone knows, it’s the only copy of the game in existence.

SUPER NINTENDO ENTERTAINMENT SYSTEM

Although not quite as ubiquitous as the NES, the SNES was still a very popular game console. With more than 700 titles for the SNES fan to collect, there are bound to be a few that demand a high price.

4. EXERTAINMENT MOUNTAIN BIKE RALLY & SPEED RACER COMBO CART

Price Range: $1,500 - $3,700

Why So Expensive? Back in 1994, the exercise equipment company Life Fitness released the Exertainment System. As the cheesy name implies, it was a combination exercise bike and entertainment system with a TV screen built into the console. Now gym rats could watch regular cable television, Life Fitness exercise programs, or play games on the built-in Super Nintendo using specially designed controllers split between each handle of the bike.

There were two games made specifically for the Exertainment System: Mountain Bike Rally, and Speed Racer, based on the popular Japanese cartoon. While Mountain Bike Rally was available as a standalone cartridge, Speed Racer was only available as part of a combo cartridge that also included Mountain Bike Rally. Gym owners could buy either of the cartridges with the Exertainment cycle, but they could be purchased through retail outlets as well. Of course the bikes were expensive and very few people had one in their homes, so the retail versions mostly went unsold. As the Exertainment cycles were replaced by newer equipment, most owners simply threw the cartridges away since they weren't compatible with a regular SNES. Naturally, this means they’re pretty hard to come by today.

While a loose copy of the Mountain Bike Rally cartridge sells for about $25, a factory sealed retail copy can go for anywhere between $50 and $350. But it’s the combo cartridge that is especially valuable with completist SNES collectors, bringing in over $1,500 for a loose cartridge, and nearly $3,700 for a factory sealed copy.

5. SUPER COPA

Price Range: $400 - $6,900

Why So Expensive? The story of Super Copa is a bit confusing for collectors: The game was a South American version of the North American soccer game, Tony Meola’s Sidekicks Soccer. Released in the mid-1990s, it’s merely a decent soccer game for the SNES. Although it was available in South America through a distributor named Playtronic, there is a second version of the game with different box and label artwork, that doesn’t include the Playtronic branding anywhere. This has led some to speculate it was also released in North America by a different company, American Softworks.

Whether it was released here or not, the alternative version of the game is hard to find, so naturally collectors are clamoring for it—so much so that bootlegs from Brazil have started cluttering eBay, making buyers wary of spending too much on a loose cartridge. However, if the original box is part of the auction, the prices can go as high as $400. And, if the auction is a factory sealed copy in exceptional condition, it could fetch as much as $6,900.

6. NINTENDO POWERFEST 1994

Price Range: $10,000 - $10,988

Why So Expensive? Much like the Nintendo Campus Challenge, 1994’s Nintendo PowerFest was a traveling competition where the best SNES players across the U.S. got to show their stuff on timed versions of three different games: Super Mario Bros: The Lost Levels, Super Mario Kart, and Ken Griffey, Jr. Presents Major League. The person with the best score from each city was later invited to come to San Diego and compete at the Nintendo World Championships II.

For the tour, 33 specially designed cartridges were produced. At the end of the tour, the cartridges were returned to Nintendo and reused for parts. Well, most of them anyway. One cartridge was found by Rob Walters at that legendary garage sale, and was thought to be the only one in existence for many years. The cartridge eventually made its way into the hands of collector Rick Bruns, who participated in PowerFest when he was a kid, making it all the way to the San Diego finals. Bruns paid $10,000 for this one-of-a-kind cartridge in 2006.

Much to everyone’s surprise, another copy resurfaced in 2012; however this cartridge was actually the first version of the game. In the early days of the competition, a home run in Ken Griffey, Jr. was worth 10,000 points, which wasn’t a lot in the grand scheme of things. So Nintendo found that most players focused on the Mario games to rack up points, and neglected the baseball game. To convince players to take Griffey more seriously during the finals, they changed the score to one million points for a home run. Bruns had a one million-point copy of the cartridge, but the new one was a 10,000-point version.

The second PowerFest cartridge was sold in January 2012 to J.J. Hendricks for $12,000. Hendricks turned around and put it on eBay in 2013 and received bids up to $23,100. Unfortunately, the high bidder backed out, and when Hendricks tried again in 2014, he was disappointed to see the cartridge had actually lost a little bit of value, only reaching $10,988 in the second auction.

ATARI 2600

The wood-grained granddaddy of home video game systems still has a rabid fanbase. There were a lot of fly-by-night companies getting in on the video game craze, which means there are a lot of rare carts out there for fans to collect.

7. AIR RAID

Price Range: $3,000 - $33,433

Why So Expensive? For many years, Air Raid was an enigma for Atari fans. The game in the strange, blue case with the unusual “T-handle” design had appeared around 1984, but no one who owned the game had a box or instruction manual to go with it. There were rumors that said it was the one and only game produced by a company called “Menavision” (or perhaps “Menovision”). In fact, collectors weren’t even sure if Air Raid was the correct title of the game because it’s not found anywhere on the cartridge. The mystery, as well as the fact there were only 12 known copies, made it a must-have for serious Atari collectors.

But all that changed in 2010 when Tanner Sandlin read a previous version of this article over on CNN.com. He recognized that signature blue, T-handle case on the cartridge, and dug through a few boxes in his garage, finding the thirteenth known copy of Air Raid—complete with box. By the time his eBay auction ended, Sandlin’s copy of Air Raid sold for an incredible $31,600.

Another boxed copy of Air Raid was found in 2012 by Harv Bennett, a former drug store manager whose store sold video games back in the 1980s. Bennett was given a copy of Air Raid by a salesman and had kept it among a small treasure trove of boxed Atari games in storage ever since. Much to Bennett’s surprise, when he opened the box, he found that he also had the instruction manual. The manual made Bennett’s the first “Complete In Box” (CIB) copy ever found. He put the game up on GameGavel.com, where it ended up selling for $33,433.

8. RED SEA CROSSING

Price Range: $10,000 - $13,877

Why So Expensive? In 2007, a new user logged into the forums on AtariAge.com and asked about a game he had recently picked up at a garage sale for 50 cents. The game was Red Sea Crossing, in which the player took on the role of Moses crossing the Red Sea, dodging fish, turtles, and the occasional arrow fired by a pixelated Egyptian. There was no box and no instruction manual, but the game label did have a company name and an 800-number that was used to identify the creator, Steve Stack.

One of the forum members found Mr. Stack, who confirmed he had created the game in 1983 to sell to the niche market of Christian households. Stack said it was the only game he’d ever made and he only had a few hundred cartridges manufactured for distribution exclusively through mail order. He couldn’t remember how many had sold, but admitted that it wasn’t very many. Unfortunately, he didn’t know what had happened to the unsold cartridges, so there was a very real chance that the one that had been purchased at the garage sale was the only one left.

With the game’s history confirmed, the AtariAge fans were salivating over what the new owner was going to do. Much to the surprise of everyone, the owner sat on the game for five years, before finally auctioning it off in 2012 on GameGavel.com, where the one-of-a-kind game sold for $10,400.

News of the auction made the internet rounds and Travis Kerestesy and Roey Lebkowitz, the owners of Medium Bob’s Curiosity Shop in Philadelphia, realized they had a copy of this very rare game sitting in their store window with a $50 price tag. Just a few days after the first Red Sea Crossing auction ended, they put their copy on eBay, where it sold for $13,877. No new copies of the game have surfaced since then, but it’s entirely possible that another one is out there somewhere just waiting to be found.

9. ATLANTIS II

Price Range: $5,000 - $7,000

Why So Expensive? It’s never mentioned in the same breath as Pac-Man or Donkey Kong, but Atlantis was a pretty popular game in 1982. The gameplay was similar to Missile Command, with players defending their base from overhead attack by enemy ships. The developer held a tournament called Destination Atlantis, where players were invited to send in photos of their TV screens displaying their high scores. The best players were then sent Atlantis II, a special edition of the game that featured faster enemy ships worth fewer points, making it harder to get a high score, but easier to determine the true champions.

Because this version was not mass produced, it’s pretty rare today. But if you find a copy of the original Atlantis at a garage sale, it might be a good idea to pick it up anyway. The competition cart had the exact same colorful label as the regular Atlantis, but had a small, white sticker slapped on the front that read Atlantis II. The label was easily peeled off, so a quick Google search will show you how to determine if you bought a $3 Atari game or a $7,000 one.

10. E.T.: THE EXTRA-TERRESTRIAL

Price Range: $5 - $1,537

Why So Expensive? There are actually more valuable Atari games out there, but this one is a bit unusual, so I’m throwing it in as a bonus for you.

The Atari video game adaptation of Steven Spielberg’s blockbuster film is often considered one of the worst video games in history, and is usually credited with bringing down the entire industry in 1983. The story went that Atari had so many unsold copies of E.T. that they had no choice but to bury them all in a landfill in Alamogordo, New Mexico, hiding their shame for eternity.

That is until the games were dug up in April of 2014.

The game’s terrible reputation has become legendary among gaming enthusiasts, so much so that the copies of E.T. that were unearthed from the landfill are now, ironically, considered collector’s items. In all, 792,000 games were excavated, not just E.T., but also dozens of other Atari titles like Missile Command, Asteroids, and Defender, and are now the property of the City of Alamogordo.

The city decided to sell hundreds of the cartridges on eBay with many of the rest being donated to museums around the world. The first round of 100 games went live on eBay in November and brought in over $37,000, with the highest bid coming in at $1,537 for a mangled copy of E.T. that had been buried in a garbage dump for 30 years. The final round of auctions ends soon, so now’s your chance to grab this dirty (but fascinating) piece of video game history. If you want to buy a non-landfill E.T. for some reason, it can be had on eBay for about $5.