And is it worth trying to recreate one? I would imagine it's already too saturated. Either way, I was mostly curious about how much these guys actually make (margin-wise). If anyone had some insight on this, I'd love to hear.
All the big gambling sites are making loads of money, however this can't be said of small and mid size online gambling sites. It takes quiet a while before your brand gets established, plus you'll incur marketing expenses, getting users to trust you won't happen overnight, it'll take quiet a while.
No one can give you any accurate amount, but if you want to judge their earning see their bets on a average basics, you'll get an idea.
If you're planing to interpret what they have done, I would advise you against it, it's over saturated plus you won't be able to offer the promotional deals for long, and if you pay late even by a day your casino will be labeled as a scam.
Gambling business is not for newbies, if you plan to start a gambling casino, make sure you get an experienced person on board to help you.