Barry Bonds' record-breaking home run ball will be sold online, and fortunate fan Matt Murphy figures to be a half-million dollars richer.

The 21-year-old New York man said today he had no choice but to sell the ball — several people told him he would be taxed on the souvenir just for holding on to it.

"It wasn't hard," Murphy said. "It was simple math. I'm upset by the decision I had to make. ... I wanted to keep it. I'm young. I don't have the bank account."

Bonds broke Hank Aaron's record of 755 with a shot into the right-field seats on Aug. 7 against the Washington Nationals.

Sotheby's/SCP Auctions will handle the sale at www.scpauctions.com beginning Aug. 28 and going through Sept. 15. The starting bid has not been determined, and auction officials estimated the ball would bring at least $500,000.

Murphy plans to share at least some of the proceeds with a friend who attended the Giants game with him. They were in town for a brief stopover on a trip to Australia when Murphy wound up with the lucky prize.