Let's not talk about prizes. Talk about structure.
(as for how often they are held... less hassle = higher frequency, or future other GMs may host it. I personally dislike pvp and that is well known fact about me, so I only host it if I'm kicked in the butt to go do it most of the time. However, perhaps other GMs who like more more than me will be persuaded to host it much more often ^_^)