At first I didn't like the idea of money going into cash prizes rather than into game development even though I'm in a pretty good position to win a cash prize.
However, by offering cash prizes more people might join and keep playing AH. This will increase funding going into HTC, and therefore by giving out $, HTC might get more $ in return.
So in the long run, I think it's a great idea. If it works, there will be more $ to spend on development and it'll make the game a bit more fun. WTG HTC.