Boxing has been around for centuries and has set a foundation of sponsors, UFC is a privately-owned organization that hasn't been around for too long (founded November 1993). This is a big part of why UFC fighters don't earn as much per fight as boxers.

It's estimated that the highest payout for a UFC fighter was $5 million. There's no information on who received all that money as the UFC does not have to release this info as it is a privately-run company.

However, the MMA Manifesto website found that Rashad Evans has earned almost $800,000 from January to September 2013.

Meanwhile, Floyd Mayweather recently earned $41.5 million for a single fight. Much of this came from the efforts between individual fight promoters to stage the event and the need to pay him this money just to get into a high-stakes fight. Pay-per-view sales also play a good part in the earnings as the fighters typically earn a part of what the event is marketed for.