The average MLS player is making 150,000 a year. I doubt it is worse. We don't have numbers, but I would bet that the MLS players get a greater share of revenue, than UFC fighters do.
The MLS salaries are right on the MLS website, they aren't making $150K a year, many are making $40K and below a year. We also don't know what other compensation UFC fighters get besides their disclosed fight pay, its widely known they make more than what is disclosed. Add that to the fact players are limited to sponsors, baseball players can have 1 that pay them and provide them with bats, gloves and cleats, football players where league mandated gear and basketball they can use their own sneakers as sponsorship, the UFC allows fighters to plaster names, websites and pictures on their shorts, shirts, hats and banners as well as shout out sponsors after they win fights.