Why should any fighter make millions upon millions of dollars
Before money came into MMA, guys were happy to fight for a few hundred bucks. Today, any UFC pro can make enough money to sustain themselves and their families and the top pros are making enough to be considered millionaires.
That said, by creating a situation in which MMA is quickly becoming mainstream and there are consistent events for fighters to participate in and where the sport is sanctioned in more places than ever and more/bigger sponsors are getting into it, the UFC is making it possible for fighters to make more than ever.
If the same model that boxing uses had been adopted in MMA, it would probably be dead by now or at best be relegated to underground matches and crappy organizations that notoriously rip off fighters.
The problems with money and greed started when MMA exploded and every fighter that used to just get ready for a fight themselves or at their school/academy started recruiting 'camp's or team's to train them, now the fighter has 5 guys on the payroll for that live and sleep with him for 6 weeks, you have a coach, manager, muay thai coach, jiu jitsu coach, nutritionist, additional training partners, strategy makers/planners, etc.
it's gotten ridiculous, this is actually why I've lost interest in MMA over the last 10-15 years, it's not really MMA anymore, now a fighter has 8 weeks notice, he knows who he will fight, can study their tapes and old fights, there's nothing raw or original about it, that's why I always like the Pride Grand Prix's!!! that stuff was killer, it was unpredictable , raw and the fighters couldn't prepare and study who they were gonna fight! it was AWESOME.