It's a gambling fallacy that this style of betting (called the "Martingale" system) is actually profitable. Basically, if you have 1.5m to play with, you will get to play 4 games until you lose all of your money. So that gives you a 15/16 chance of making 100k and a 1/16 chance (LLLL, all at 1/2) of losing 1.5m. So, on average, you will win 15 times (1.5m total) and lose once (-1.5m). Interesting. Though, say you've got 10 billion gp. If you restrict yourself from using only 100m, this could work. In the rare case that you happen to lose the 100m, just keep doubling it, and after a few more games, you should have gained it back. Nope, same thing. You always have a chance of losing ALL of your money that is exactly proportionate to the expected payoff for all of the small wins you will make. No matter how you try to break it up, the only way to make money in a 1/2 chance game is to get above-average luck.