In late August, Beijing resident Zhang Dongqi received the exciting news: His new sneakers were ready for him to pick up — in Shanghai.

Few would consider making a five-hour, thousand-kilometer (620 miles) journey just to buy two pairs of shoes, but Zhang headed straight to the train station without a second’s thought.

The 25-year-old had good reason for thinking the trip would be worthwhile. The limited-edition Undefeated Nike Kobe 4 Protros he was about to purchase were among the most exclusive sneakers in the world, coveted by collectors across China. And, more importantly, they were an excellent investment opportunity.

Zhang had won a lottery organized by Nike’s China distributor ahead of the new line’s release, making him one of the few people in the country able to buy the Kobes at their retail price of 1,399 yuan (US$196), Caixin reported in a special feature.

Within days, he would be able to resell them for up to 4,000 yuan, as China’s sneakerheads scrambled to get their hands on the ultra-rare purple-and-yellow shoes, created to celebrate basketball legend Kobe Bryant’s 41st birthday.

An enormous secondary market for special-edition sneakers is emerging in China, fueled by the growing popularity of street fashion and digital platforms that allow sneakerheads to trade shoes like stock market shares. The market has become so hot that it is even attracting professional investors who previously traded in other speculative assets like bitcoin, raising concerns of a sneaker bubble, the report said.

Though the United States remains the global center of sneaker culture, demand for rare designs by Nike and Adidas is growing even faster in China, where hip-hop and basketball are hugely popular. According to Zhang Qi, chief analyst at online consulting firm iiMedia, China’s secondary market for sneakers exceeds US$1 billion and has been growing 35% year-on-year.

Much of this growth has been driven by sneaker obsessives like Zhang Dongqi, who has been collecting shoes for nearly four years. “I’m an impulse buyer,” he tells Sixth Tone. “Once I set eyes on a pair, I want to buy it right there and then.”

Like many sneakerheads, Zhang, who works in finance, subsidizes his hobby by buying up multiple pairs of newly released designs and reselling the extras for large markups. He does this using Poizon, a Chinese trading platform that specializes in sneakers, the report said.

The Chinese app provides a similar service to U.S. platforms StockX and Goat, which have yet to gain traction in the mainland market. The platforms have accelerated the boom in sneaker reselling by making shoes nearly as easy to trade as financial assets.

Until late September, Nice, the main competitor to Poizon in China, even allowed users to view trend charts tracking the performance of various sneaker ranges.

This is attracting a whole new class of traders to the Chinese sneaker market, who often have little interest in the products in which they are investing. Poizon had an estimated 1.4 million monthly active users this March and is valued at over US$1 billion.

Dylan, a 25-year-old financial worker from Shanghai who requested anonymity, was among the first Chinese investors to take the sneaker market seriously.

He first heard about secondary trading when he listened to a TED talk by StockX CEO Josh Luber four years ago, while he was studying finance in the UK. He started dabbling in the market soon after, and then quickly switched to trading larger volumes, the report said.

Dylan’s account balance on Poizon testifies to his success: He has earned more than 1 million yuan in the past 10 months. But he warns that the market is becoming increasingly volatile, as media reports regularly exaggerate the profit margins sneaker traders make.

Though it is sometimes possible to earn 400% returns on a pair of shoes, this only happens in extreme cases, according to Dylan. More often, margins are in the single digits or double digits, he says.

Zhang Yi, the iiMedia analyst, tells Sixth Tone that the market is becoming polarized as increasing numbers of young people and professional speculators jump on the sneaker bandwagon.

“I worry about the youngsters who recently entered the market,” says Zhang. “Their financial background is not strong enough.”

Poizon and Nice appear to be waking up to the risks posed by the influx of new money. In September, Nice removed the trend charts from its app. Both platforms have placed banners on their home pages saying they oppose price manipulation.

“There’s definitely going to be a bubble,” says Zhang Yi. “The only question is when it’s going to burst.”