Well there is prizes for placing you know. Let's see, don't pay and watch tibbs win another $500 this month or do play and maybe beat him or whoever out for it, easy choice for me. I suppose if you felt like you didn't have a chance it would be different. But given the current state of the game, alot of these tourneys could be won by any number of people.
Anyway, if you goto the leaderboard, that is essentially a list of who payed in to play.