The US Open has featured dazzling performances from Coco Gauff, Madison Keys, Carlos Alcaraz, and Ben Shelton, but mainly deep-pocketed tennis fans could afford to watch the action in Flushing.

Tickets for the Grand Slam tournament have been selling for a pretty penny on the secondary market — with courtside seats asking as much as $20,000 per person while a spot in the nosebleed section will set one back more than $700, according to Bloomberg News.

Even the price of lower-tier grounds pass, which includes general admission to matches between lower-ranked players but does not include access to the Arthur Ashe Stadium, where the higher-ranked players compete, frequently surpassed $200 on Stubhub.

Marc Viscardi, a transplanted Arizonan who has lived in New York since 2010, has made it a point to attend every US Open tournament since moving East.

He told Bloomberg News that he paid almost $300 for a ticket in the same part of the stadium that 12 years ago cost him $79.

“This year, the prices felt that much more audacious,” Viscardi told Bloomberg News.

“It’s rare that the price of an event or concessions jumps out because we don’t have the same sticker shock living in New York, but this year it really did.”

A freshly made cup of coffee from Lavazza can cost between $8.25 and $9.50 depending on the size.

A single-scoop cup of ice cream from popular brand Van Leeuwen will set one back $9.50 while a double scoop goes for $11.50 — with the option of adding a waffle cone for an extra $2.

A steak sandwich goes for $26, a chicken sandwich is priced at $19.50, and a milkshake will set you back $12.

Fans can still score seats through Ticketmaster at a more reasonable price for tonight’s women’s semifinals — which will feature Gauff taking on Karolina Muchova of the Czech Republic in the first match at 7 p.m., followed by Keys against world No. 1 Aryna Sabalenka of Belarus. The cheapest seats cost $159.

The men’s semis, slated for Friday, have tickets available beginning at about $250. Alcaraz, the sensational Spaniard, will face Russian powerhouse Daniil Medvedev while Shelton squares off against Serbian legend Novak Djokovic, who is aiming to win his 24th Grand Slam singles title — the most of any male.

“The US Open is a cultural phenomenon and demand is at an all time high,” Chris Widmaier, a spokesperson for the United States Tennis Association, which oversees the US Open, told The Post.

Widmaier said that the prices of tickets on the secondary market are “dictated by supply and demand and by market forces.”

The skyrocketing prices “show how desirable attending the US Open has become.”

“That being said, when we set our prices we set them at levels to provide access for everybody,” Widmaier said.

“You can get tickets for as low as $30 to the US Open. Those tickets sell out quite quickly.”

The high prices haven’t deterred fans from flocking to the USTA Billie Jean King National Tennis Center at Flushing Meadows to take in the action.

The first week of the US Open drew 502,385 spectators — the first time the tournament’s first seven days eclipsed the half-million mark in attendance.

The US Open set a Labor Day attendance record, drawing 201,787 fans, according to Sports Business Journal.