People keep whining about the pay base for MMA and using boxing as an example... nobody is bothering to look and see that those no-name guys, under card fights (unless it's like a co-headliner) don't make much more than the UFC undercard guys.
Here's a link (which I've read before on this topic) which gives you the numbers for a comparable fight card in boxing and MMA from 2005/06
UFC puts boxing on ropes except in fighters' salaries - Boxing Scene Forums
The article talks about how much more the fighters in boxing get... but if you add the two main event salaries together, and subtract them from the total fight card purse, the under card paid out about the same amount of money.
The Morales-Pacquiao fight had a total card purse of 4.66 million and paid 4.5 million to Morales and Pacquiao.
The Liddell-Couture fight used in comparison had a total card purse of $656,000 with $475,000 going to Chuck and Randy.
So the only thing people can complain about really, is that the big names aren't getting the money they should. Not that the little guys aren't getting squat compared to the main event guys.
There's a reason the low-level guys get paid low amounts... it's thinning the herd. If you're willing to get punched in the head over and over again for $2,500 than you show your stuff.
If you win you move on to more money.
Just like boxing.
If you lose, you either keep making that 2G's for getting slapped around or you quit.