I was never much into gambling, but I loved it when Primedice (or was it Stake?) had a EV+ promotions. I think it was winning 0.05 BTC for a challenge that would take losing about 0.006 BTC to reach.
I also remember the days when 0.002 BTC withdrawal fees were more or less necessary to pay for the on-chain fee, but nowadays that's ridiculous. Some exchanges took a long time to lower their withdrawal fees, but even they followed. Both casinos and exchanges have one thing in common though: withdrawals are not in their interest.