If you have more than enough money, i don't think you will risk big amounts by gambling, may be rich people gamble just for fun with small amounts.
Depends on the rich people, some rich people like to play big but some others do not like it. If there is no rich people play big amount, so who are the one who wagered such a big amount in single bet on some gambling sites? They must be rich people, poor will not able to bet big.
Tes it depends on their mindset, few rich people will not take the risk so they will play with a small amount just for fun, But some people will play to make so they will take a chance with a big amount. They are ready to afford their loss. Suppose if they win that bet means it is a big profit for them. If I am rich I will not play for fun, and I play for big profit.