Speaking from experience on consulting for shows, the fighters' purse is actually the biggest overhead next to the venue rental. Then comes the marketing, production, insurance, hotels, food, transportation, extra security, etc. It's an extremely tough business. But my experience was very rewarding. Sad to see these companies fold; Bodog, Elite, Affliction, WFA, IFL, etc.
What I don't get is how they lose money when they have 50,000 spectators. Wonder what their PPVs are. They should be getting huge sponsors like Toyota, Honda, Asahi, or some corporate title sponsor.
Man I can't even tell you how sound the UFC business model is.