So money may makes 1000x more than mama fighters because he does all the heavy lifting and has crunched all the numbers?That's a question of economics.
If I were his manager, I would put in the time to get the numbers and start making comparisons and put a value on performance as a way to generate future interest (fan investment). But it's not my job and it would piss off the people I work for if I devoted a large part of my working day to figure this out. However, I am confident with regards to how we should determine a fighter's worth to a company.
Getting the UFC to pay fighters what they're really worth is impossible at this point because you have too many employees who are making careers off the fighters. Those people will command their salaries based on what that position can earn elsewhere, fighters don't have an elsewhere i.e. you have a lot of people "honestly" exploiting the people who do all the heavy lifting. You need a new organization that comes from the fighters leaving en masse. Ideally it would be a fighter co-op type organization. It's insane how many sycophants, snake-oil salesmen and cunts there are in this world.