An example of it being used literally. You and I play a round of golf every week and we usually bet $10 on each hole. Do you want to double the stakes this week? Play for $20 a hole today?

I'm pretty sure it's derived from gambling (as mentioned). So it means that one is increasing (or doubling) the risk, for the possibility that it pays out in the future. Like the more money you bet, the higher the stakes. In other words, you are risking to lose money in order to win money. I hope that made sense. It was harder to explain that I expected. ㅋㅋ

I think, what "the answer is on the surface", like saying in my country:) Probably "double the stakes" means "I'm very sure in my actions", like in poker "I'm all in".