Bodog's Casino Bonus

[Hawklet]

Okay so Bodog offers a 20% deposit bonus on every deposit. But to clear it at the casino you need to wager 20x the deposit and the bonus.

Their craps game has a .606% house advantage with optimal strategy.

So if you deposit 100 dollars, you get a 20 dollar bonus and must wager 2400 to clear it. So 2400 * .99394 return ~ 2385. So you keep 5% of your bonus.

The bonuses are infinite. Is my math wrong? How can they offer this without being exploited?