Before eBay, people who collected sneakers mostly scoured shop bins and garage sales in hope of finding something good. The searches were arduous, and limited to the collector’s geographical area. But then the online auction site launched in 1995, offering a single, addictive, worldwide focal point, accessible at any time and from anywhere, for people who wanted to sell their stuff, whether old laser pointers or Nike Air Jordans. Everything changed, and a market began to grow.

Today, the numbers point to a growing, and increasingly globe-spanning, population of eBay-enabled sneaker collectors. Their spending on sneakers purchased over eBay has grown by double-digit percentages each year since 2010. Last year about 6.3 million pairs of sneakers were sold on the site. Of those, 1.2 million were priced at $200 or more, pushing total sales of those pricier models past the $400 million mark, and making them one of eBay’s top 10 fashion categories, according to Marcelle Parrish, eBay’s head of fashion.

“Ebay is what gave birth to the sneakerhead world,” says Jordan Geller, who in 2012 was recognized by the Guinness Book of World Records as having the world’s largest sneaker collection, at 2,388 pairs. “There were always people that were into sneakers and there were sneakerheads, but we never had a way to connect.”

Those connections have created a network of sneakerheads (as the most knowledgeable or dedicated of collectors are known) that continues spreading across the US and the UK and is now reaching into emerging markets. In the last five years, those established sneaker markets have at least doubled in size—the US has more than tripled—while emerging sneakerhead markets such as Italy, Russia, India, and Mexico “have tripled, quadrupled or better,” Parrish says.

Europe, particularly the UK and Germany, lead the way in terms of overall sneaker sales on eBay, with the US slightly behind.

Parrish points out that the market in the Asia-Pacific region, and particularly China, is growing as e-commerce becomes more widespread there.

So what are all these sneakerheads buying? In a word: Jordans.

In 2013, Nike Air Jordans accounted for $1 in every $3 spent on sneakers on eBay. Of the more than 1,300 sneaker models that sneaker-data site Campless tracks on eBay, eight of the top 10 models in terms of dollar sales between March 2014 and February 2015 were Jordans. All 10 of the top selling sneakers on eBay—including those Air Jordans—were made by Nike.

Sneaker Style Total dollar sales 1. Air Jordan 11 Retro Legend Blue $3,774,359 2. Air Jordan 6 Retro Carmine 2014 $2,910,015 3. Air Jordan 11 Retro Low Concord $2,671,536 4. Air Jordan 11 Retro Gamma Blue $2,531,279 5. Air Jordan 11 Retro Playoffs Bred 2012 $2,508,553 6. Air Foamposite Pro Yeezy $1,924,504 7. Nike Air Yeezy 2 Red October $1,739,232 8. Air Jordan 6 Retro Infrared Black 2014 $1,696,121 9. Air Jordan 11 Retro Concord 2011 $1,496,863 10. Air Jordan 11 Retro Low Infrared 23 $1,364,494

Ebay’s presence in the market does have its drawbacks. Sneaker flippers are notorious for buying up desirable sneakers when they’re released and then reselling them on the site at inflated prices. People who can’t pay up end up missing out.

It’s the consequence of supply and demand in a market with few rules and a rapidly growing number of buyers.