In reality, the UFC doesn't need them. The UFC's biggest star is Dana, and all their money will come from media rights fees, sponsorship deals and live gates which their name sells alone. I too prefer they would pay up to sign these guys, but it isn't their MO to do so and hasn't been for a while. They're very particular about which guys they'll sign. The UFC may have the highest concentration of top guys, and will for a long time, but they don't have all of them, by their own choosing.
TKO has even spoken about possibly getting out of the PPV business and selling it to a provider if the money is good enough. I'm very curious how much money they're going to get in their next deal as both Amazon and Netflix are getting into live sports content, and WBD's sports portfolio is lacking if they lose the NBA.