Serena Williams' smashed US Open racket auctions for nearly $21G -- after ball boy sold it for $500

A tennis racket Serena Williams famously smashed during an argument with the chair umpire before her loss in last year's U.S. Open to Naomi Osaka has sold at auction for $20,910, according to Goldin Auctions.

Williams threw the racket after the umpire ruled she had received illegal coaching, which gave her a second violation. She incurred a third violation for verbal abuse when she called the umpire a “thief,” insisting she has never cheated in her life.

SERENA WILLIAMS FINED $10,000 FOR REPORTEDLY DAMAGING COURT AHEAD OF WIMBLEDON

Williams was fined $17,000 for the violations, which included $3,000 for breaking her racket.

After her loss to Osaka, Williams gave the smashed racket to ball boy Justin Arrington-Holmes who sold it for a mere $500, The New York Times reported.

“Looking back I wish I’d had someone help me with the process,” Holmes told The Times. “I was not familiar with how any of this works. I just wanted to get rid of it.”

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Jesse Owens' 1936 Berlin Olympic gold medal also sold at the auction for $615,000.

Williams was fined $10,000 this year for damaging a Wimbledon practice court when she threw her racket before the tournament started.