Whatever fights are on the main card. It's usually 5 fights, I think. This last one had a pretty weak card and I'd be surprised if it sold well.
I would never consider paying that much to watch a fight, since there are a number of area bars where you can see it for free, a friend of a friend works for the cable company and hosts them all for free, or you can sometimes find them on the internet. And if it's really fantastic, I can rent the DVD months later and copy it.