Caitlin Clark’s new Nike sneakers sold out almost immediately on Tuesday. Secondary market sellers are already getting up to $600 for the Kobe V Protro model. That’s significantly higher than the $190 retail price.

Need another barometer of how popular Caitlin Clark is with basketball fans? Her version of a popular Nike sneaker sold out in minutes when it became available for the first time on Tuesday.

And, predictably, the secondary market is already the shoes for a huge markup.

Nike released the Kobe V Protro—in the navy blue, red, orange and yellow colors of Clark’s Indiana Fever—at 10:00 a.m. ET. But before most people could put them in their cart, they were gone.

The retail price was $190. But if you want a pair now, brace yourself. Prices on Ebay are generally hovering between $350 and $400 per pair, with at least one buyer paying $600.

Clark signed an eight-year deal with Nike in 2024 that was reportedly worth $28 million. That followed a two-year deal between the two signed in 2022.

Clark has been a phenomenon since her college days and her entry into the WNBA has boosted both ratings and ticket sales. Last season, the league saw its highest attendance in 22 years and had the highest viewership in 24 years.

Clark isn’t the first WNBA player to get her own line of shoes. Sheryl Swoops was the first to do so with a line of Nike Air Swoops. Sabrina Ionescu has also introduced the Nike Sabrina 2s.

But Clark’s shoes are, by far, the most coveted among sneakerheads. And there’s lots of room for prices to go up.

Two years ago, a pair of Air Jordans worn by Michael Jordan in Game 2 of the 1998 NBA Finals sold Tuesday for $2.238 million, the most ever paid for a pair of shoes.

This story was originally featured on Fortune.com