It was brought to light by a lot of people but most notably by Jake Paul about how UFC fighters are not paid a "fair" amount of what the promotion brings in at the various events. Many ex-fighters have stated after they left or were released by UFC that they would encourage other MMA fighters to do anything other than fight in the UFC because of this. It is easy to look at some of the payouts from UFC events and some of the superstars that have become very wealthy because of UFC and think that this is a very lucrative sport, but that is the exception, not the rule.
Ex-fighters have stated after leaving UFC that they wanted to speak up when they were still with the promotion, but feared they would be let go if they were to say anything - which is understandable. Dana White and others at the top of UFC management have dodged this question, scoffed at it, and become very upset when any reporter even brings it up and latest Pay-Per-View figures and financial compliance statements make a good point for the fighters that continue to complain about the fact that UFC doesn't pay out enough to the actual fighters, and keeps a lion's share of the money for themselves.
UFC 305 certainly wasn't the most exciting card of the year, that's for sure. It was a major event though with a sold out crowd in Perth, Australia that featured some big names and one would expect, some big fight purses. This assumption would be incorrect though and there is a reason why they don't talk about what the fighters were actually paid. Dricus Du Plessis defeated Israel Adesanya in the main event to defend his championship and of course he was very excited about this submission victory over one of the most celebrated middleweight contenders of all time, yet his fight purse for this impressive victory? Well it was a mere $42,000. If we go further down the card to a heavily promoted heavyweight fight between Tai Tuivasa and Jairzinho Rozenstruik, we see that these two were paid $16,000 and $11,000, respectively.
EDIT: IT turns out and was pointed out by 
Now to the uninitiated this might sound like a lot of money to be gained from 15-25 minutes of work but this is a very misguided notion. As a top-tier fighter, you can only do around 3-4 fights per year and the camps that you train with and the expenses associated with simply being alive, this is NOT a good wage.
The total promotional payout for the ENTIRE ROSTER on UFC 305 was under $300,000. Now UFC doesn't have to report their total take from events but lets just think about the sold out arena in Perth and the fact that it costs hundreds of dollars per seat at these events generally speaking and then factor in the hundreds of thousands of pay-per-view buys that regularly happen for these events. It is easy to assume that the "house take" at any of these events is always going to be in 8 digit territory.
UFC gets away with this by being the biggest and some would say the only real name in global MMA. On a pay-per-view card, some of the fighters were paid a mere $4000, win or lose.
Imagine if you are one of the guys or girls on the undercard and this is going to be one of your 3 to 4 fights a year and let's imagine further and think that you get offered this many a year. Congratulations! You now make $16,000 a year! I don't know what sort of country that it is even possible to live off of that much money, but it can't be very many of them.
If you want to have a look at the full press-release compliance report of purse payouts for the most recent UFC event you can see it here.
To me this is scandalous and people really need to be talking about this more than they do. I have said to friends of mine that I feel as though the quality of UFC has gone down in recent years and this very weak payout structure is likely a very big reason why that is the case. While McGregor and Jones are getting millions for every fight, a vast majority of the people on these cards, who are global celebrities of sorts, are making less money than an assistant manager at a fast-food joint.
I suppose this is a very large part of the reason why almost all of these guys seem to be seeking out boxing promotions such as Jake Paul's, on a regular basis. This greed on the part of UFC is allowed to continue because they are the only game in town.
Now, I've recognized that a great deal of what I have said above has turned out to be misguided information on my part and for that I apologize. It is important to note that one person on the main card was paid very poorly and that the people who participate in non PPV events are regularly barely paid despite the events being quite expensive to attend. These events are kind of treated like bands playing for free for self-promotion purposes.
I'll need to be more careful in the future. Du Plessis was actually paid $500k, not $42 like I stated above, so I guess he has a good reason to be smiling. I'm gonna sit the next few plays out because I made a terrible mistake here :)