According to ESPN, Mayweather approached a sports betting vendor in Las Vegas around 3.30pm – just hours before the main event – and tried to stake around £310,000 on the fight ending inside 9.5 rounds. The odds were 1/2, meaning he would have make a £155,000 profit, but the bet was not placed. Concerns over the legality of a fighter betting on anything other than a straight win reportedly caused a delay. He then tried to bet on himself to win by knockout but was again frustrated by the delay and left without staking any money. Source:
He was p*ssed.