Many corporations are looking to pull a fast one on consumers, but some of them actually rely on our better virtues as shoppers to make us accomplices in their predatory schemes. They expertly use our elemental needs for convenience, â€‹speed, â€‹value, and quality against us. Here are five common ripoffs even good consumers fall for when they're looking for a dealâ€‹.

1. â€‹Certified pre-owned cars. Automakers say certified pre-owned cars are the next best thing to buying new and they’ve been very popular with budget-conscious drivers who want new-car reliability without paying the new-car price.

A certified pre-owned car typically costs $2,000 to $2,500 more than an identical non-certified car, but the extra price you pay is often more than what you’d likely spend on repairs during the car’s warranty period. So, these cars are really nothing more than used cars with an expensive extended warranty tacked onto the price.

One sales pitch car manufacturers use to sell certified pre-owned cars is that they’ve passed a rigorous inspection by the car dealership, often citing a large number of inspected items (100 or 150 are often used, perhaps because they have three digits). And while many of these inspection points may involve the frame, engine and other major components, quite a few of the items on the checklists are redundant, and some, like checking the windshield-washer fluid level, are actually absurd.

But some certified pre-owned cars aren’t looked over closely at all. One certified pre-owned car — as it was famously covered by many news outlets back in 2007 — was not one car, but two. The front half of a 2004 Chevrolet Monte Carlo and the back end of another Monte Carlo had been welded together. And it appeared that both halves of the FrankenCarlo had been involved in serious crashes.

Consumers should keep in mind that there is no industry standard to define what “certified” actually means. Any dealership, from a new-car dealer to a used-car lot, can claim a car is certified. It’s a system that depends solely on the honesty of the seller.

Automakers, through their dealership network, and used-car retailers say they’ll fix problems they find before they sell the car, but we’ve witnessed a used car, bought by the dealership in an industry auction, arrive on a car carrier only to be immediately rolled out on the lot and tagged as “inspected and certified.” When we called the dealership on this, they said they had every intention to inspect the vehicle before it was sold. Other dealerships we talked to told us they will sell any car as certified or not certified, depending on what you’re willing to spend.

The only guarantee with a certified used car is that the dealership and the automaker make more money. With relatively newer used cars in particular, certification doesn’t make much sense as most cars are relatively trouble-free in their first three to six years. Your best bet when buying a used car is to take it to an independent mechanic for an inspection and skip the in-house certification and expensive warranty and put that money into a rainy-day fund for that car if something goes wrong.

2. â€‹Gift cards. Gift cards might seem to be a nice, tidy way to give cash to someone, â€‹and some even seem thoughtful as we choose the type of store the recipient shops in. And everything comes in a nice envelope tied up in a bow. â€‹But â€‹gift cardsâ€‹ can be infuriatingly expensive. For starters, you often pay a fee when you purchase them. At one retail store, the charge is $2.50. But it doesn’t stop there: Some bank-issued gift cards charge a fee to reactivate the card after a period of inactivity. You may also be stuck with the card if a retailer files for bankruptcy protection and refuses to honor the card. You can also lose money when you buy a card that’s not reloadable and the balance is lower than the purchase price of any item at a store.

For privacy’s sake, it’s always better to give cash, as retailers and credit card companies can’t track the purchase history of people you associate with if they’re paying with greenbacks.

3.. â€‹Deli meats and salads. Buying pre-packaged and sliced deli meats off the store shelves can cost much more than when you go to the deli counter and have it sliced for you. At a major supermarket chain, a brand-name pre-packaged Virginia ham sells for $10.27 a pound, but when you buy it at the deli counter, the same brand and style of ham costs $7.99 a pound — 22% less. Among all the deli meats we checked, the price difference between the pre-packaged version and the deli-counter version was between 22-25%.

To make matters more confusing, a supermarket’s deli counter may sell the same salads, unpacked, that are also sold in tubs a few feet away, but the deli-counter versions are often more expensive. We found an unpacked egg and potato salad in the deli case cost $3.49 a pound while the identical salad sold in a plastic tub cost $2.33 a pound, about a third less. Overall, we found comparable salads available at several supermarkets to be much less expensive when sold in pre-packaged tubs, to our surprise.

4. â€‹Auto-renewing subscriptions. Many Internet services, from news hubs to dating sites, use auto-renew billing to conveniently get you to extend your subscriptions. And while they’re required by law to tell you that they’ll automatically bill you and prolong your service down the road, they usually do so in the fine print you might not see. So, even if you haven’t used the subscription in months, even years, you may notice mysterious charges appearing on your credit card or PayPal account as these zombie accounts linger on. Worse yet, these services may even raise the price of the subscription, especially if you first signed up at an introductory price.

While automatic billing might be convenient and expected for something that renews monthly — like a web hosting account or a subscription to the New York Times — companies that bill at longer intervals like quarterly, semiannually, or yearly can leave unwelcome surprises. Some states, but not all, require that companies tell you you’re still on an auto-renew schedule before billing you again. If you don’t live in one of these states, calling the offending biller may result in a refund. If not, a quick call to your credit-card company often gets your money back.

5 â€‹Unused â€‹broadband speed. Internet service providers, mostly the cable companies, are quick to sell you their next higher-speed tier. For example, Verizonâ€‹ now sells its basic Fios service, which is 25 megabits per second (Mbps) for $50 a month, but aggressively â€‹markets to users â€‹an upgrade â€‹to 75 Mbps, which costs $70. While you might think that tripling your speed for $20 sounds like a great deal, it isn’t. Most consumers fall into usage categories that need no more than 10-15 Mbps, which is fine for web browsing, downloading music, streaming videos and most gaming. So, unless you’re streaming high-definition media on several devices simultaneously, you’re likely paying for broadband you probably won’t use.

Many of the cable/ISPs had slowed down network performance for streaming services like Netflix some months back, while simultaneously marketing faster speeds to customers. In the end, it turned out that Comcast and Verizon had been purposely impeding performance of Netflix videos and have since worked out a deal with the streaming company. But in the wake of this bandwidth war, many consumers are now paying for more speed than they need, not knowing that their service was purposely hobbledâ€‹.