Can't remember the source, was either mma show or mma hour. In an interview talking about fighter pay, the individual talked about how a boxer starting their big-time pro career can get paid as little as $500 IF they win, but (for the most part) an up and coming UFC fighter making their debut is almost guaranteed $6,000 just to fight.
If you look at the distribution of money in a UFC card compared to a boxing card, the UFC is a lot less top-heavy than the boxers. Not everyone can make Mayweather money.
D. Cerrone | R. Souza | F. Werdum | R. MacDonald | M. McDonald | D. Maia | J. Mein | C. Condit
M. Coenen | S. Kaufman | A. Davis