If he can bet that kind of money then I'm sure he has back up money to shoot again to try to get his money back and some.
If he doubles up but I don't know any Vegas books has that high of a limit. They have a cap for a situation like this and to protect their interest and not having any gambler using the martingale system to get their money back.
I think South point casino in South Vegas is notorious for high limits on sports betting. MGM is also notorious for Mayweather likes to bet that much there.
They gives them a line of credit to play unlike anybody else who needs to pay up front at the window.
Whales I tell you. But the most notorious I ever heard are billionaire azn usually Chinese.