Hard to say. The amount of money someone would have to pay me to murder someone, for example, would be in the tens of millions, but I have no use for that much money so risking it feels pointless.

It would pretty much need to be so much that I could retire in a year or two - otherwise it's pretty meaningless. I'm already in the financial situation where I can afford almost anything I want, and what I want isn't that much. Most of it I already have.