Thats true the minimum bet for this challenge is just a piece of cake for whales of rollbit, money is not a problem at all. Everytime im looking in the leaderboard, these gamblers amazed me for wagering huge amount, they're really rich. So I wonder if they gamble to earn more or just for satisfaction.
With such amounts you have to have a correspondingly high stack, you can no longer do that with very many small bets. So we are most likely talking about (bitcoin) whales with a lot of bitcoins.
If you have so much money, you have usually already afforded everything you wanted to afford. That these people play to increase their stack of BTC I think is excluded, there are easier and less risky ways (Lending, ...) -> So these people play primarily just to have fun and possibly just to be able to show off when they stand at the top of the leaderboard