(Robert Prange/Getty Images)

After Serena Williams announced Tuesday her plans to retire from tennis, likely after the upcoming US Open, ticket sales skyrocketed for the year’s final Grand Slam.

In just the six hours after Williams’ announcement, which came around 9 a.m. ET Tuesday, the US Open sold 13,000 tickets, including 4,500 for opening night on Aug. 29, USTA spokesperson Chris Widmaier told the New York Post.

“You talk about the Serena effect, it’s like a tsunami,” he said. “That’s a spectacular day. In fact, it may be unprecedented.”

While tickets for the upper deck of Arthur Ashe Stadium retail for around $35 on Ticketmaster, Widmaier revealed that some are trying to resell their tickets for $7,000. Williams isn’t even guaranteed to play on that day.

Williams is a six-time US Open champion, and the New York major likely will be her final tournament, or so she implied in Tuesday’s Vogue cover story.

On Wednesday night, she dropped her first match since making her announcement at the Canadian Open. Her goodbye to that tournament kicked off her short retirement tour.