A few years ago, I believe it was Jon Olsson (by a large margin), then Simon Dumont. Now, I'm not sure. I'd be willing to bet it is still Jon Olsson, but he works for it in different ways than other pros do.
As doug said, you're probably going to look at some of the dudes on red bull, nike, and to a lesser extent, oakley guys out there. Guys who have been in the game a little longer tend to be paid more than the younger kids even if you think the new kids are "better."
Another thing to consider is that sponsors often match (or more) contest payouts. So if you win $60K at Xgames, your energy drink sponsor may shoot you another $60K. So, despite contracts, contest results may have a large effect on who is making the most.
Freeskiers don't make shit by the way. There are a very, very few number of guys who break six figures. Most are making just enough money to get by.