dave you are a weirdo.
The biggest boxing stars blow away the biggest UFC stars.
The upper level guys are about the same. For example, I recall Pavlik making about $300k on a Shane Mosely undercard. That's about the neigborhood of a UFC fighter who is a part time main eventer working a semi main event (somebody like Wandy or Rich Franklin or BJ Penn).
It's the lower guys where UFC blows away boxing. UFC lower card guys will make between $2000 bottom level to $10k-$20k or so for some guys. The undercard boxers (the guys fighting 4 rounders and such) are paid next to nothing, in the hundreds.
Don't feel too bad for UFC main eventers. Many get PPV cuts, so guys like Lesnar and GSP are banking seven figures every time out. But they arent making that Mayweather $20M.