It boggles my mind to think about the bankroll required to offer limits that high.
Well, if you look here: https://bitcointalk.org/index.php?PHPSESSID=63jvb7jar34mtdefttso41v715&topic=75883.0 you can see that some gambling games offer unlimited max bet
)There's a post somewhere in this thread about bitZino's analysis of what max bet they can safely offer. I don't think it talks about their bankroll specifically but it may be possible to infer a ballpark amount based on their current maximum bets. I'll link to the post if I find it.
I notice the post that Ignas linked to has the max bets wrong for bitZino - at least for blackjack, which it says has a 10 BTC max. I'd suggest alerting him so he can fix it.