There's always people who can outpay the UFC, When Gil Melendez first won the Strikeforce LW title he was making 30 grand a fight, When Sean Sherk won the UFC LW title he made 25 K a fight. The lure of the UFC isn't pay by a long shot, it's exposure more than anything.
I'm not sure you have any idea what you're talking about. You do realize that the UFC is a for profit business right? They are not going to pay a fighter any more than they have to. And if they get into a bidding war over a fighter, they will be able to out bid any of the current orgs. In fact, they use the bidding for fighters strategy to bury their competition. Look at what happened to EliteXc, IFL, Pride, etc. They're doing the same thing to StrikeForce now. Dan Henderson is the perfect example. They drove his price way up, forcing StrikeForce to overpay for him. Now their stuck with a guy who they paid too much for and who just lost big time. Jake Shields is next. Dana wants him bad, so I'm sure he'll get him. This will be a big blow to StrikeForce.
And you're right. The UFC does offer significantly more exposure to its fighters, which translates to significantly more sponsorship money to the fighters.