First off, how did you do your calculations? That gave you 10% chance of a gambler who isn’t rich winning a thousand odds? The probability should even be lower than 0.01% when calculated.

And another thing, if we look at it from the risk perspective, you could say that the rich have more at stake here because since gambling isn’t something you can predict the outcome correctly then it means that they’d lose more than what a poor person would lose to the casino. So if a casino is to choose between a wealthy gambler or a poor one who do you think they’d go for? It would definitely be the wealthy punter because they’ll play with larger amount and lose more to the casino than what they’d actually win.