After his 50th win, undefeated American boxer Floyd Mayweather Jr. insisted on Sunday that his match against MMA fighter Connor McGregor is his last boxing match. The 40-year-old millionaire beat McGregor on Saturday night in the 10th round of their bout at the T-Mobile Arena by a technical knockout.

He also broke the 49-0 record of boxing icon Rocky Marciano. Mayweather said his 50-0 fight against the Irish MMA fighter should not have an asterisk because “A win is a win, no matter how you get it.” Mayweather continued, “Rocky Marciano is a legend, and I look forward to going into the Hall of Fame one day,” AFP reported.

Biggest single payout in sports history

Although the guaranteed purse of his Saturday fight was $100 million, lower than the $240 million purse in his 2015 fight against Filipino boxer Manny Pacquiao, he stands to make $300 million. It would be the biggest single payout in sports history, Mashable noted.

Mayweather stands to get a substantial part of pay-per-view earnings from Showtime, estimated to be between $150 million and $200 million. Based on the nine 3-minute rounds and 1 minute, 5 seconds he fought in the 10th round, Mayweather boxed for 28 minutes and 5 seconds or 1,685 seconds. If he earned $300 million on Saturday night, it is equivalent to $178,041 per second, or double the $83,000 per second he earned in his 2015 bout against Pacquiao.

Mayweather could have earned more if he was allowed to make a $400,000 bet that he could beat McGregor – who earned more than $30 million – but he was prevented from betting on himself, according to ESPN.

50-0 commemorative caps

Ten minutes after the bout ended at 1 a.m., commemorative caps with the 50-0 markings went on sale for $40 at the stadium.

It was another attempt from Mayweather to make the most money out of his last professional fight. The money from the cap sales is expected to help the unbeaten boxer pay the IRS $22 million in back taxes, which is rather surprising because he is estimated to be worth $400 million before the fight against McGregor. The boxer’s wealth is in cold cash.

Meanwhile, UFC President Dana White claims that McGregor will return to the Octagon ring again this year, The New York Post reported. He said that fighting in MMA remains the top priority of the Irish MMA champ who won over Eddie Alvarez by TKO in November.

McGregor, however, remains open to fighting in both sports. “Maybe going forward, since I’m the king of the boxing ring and the king of the octagon already, once I’ve conquered both, maybe I’ll just my own hybrid of an octagon and a boxing ring,” he said.