And Fox would have to have several consecutive DoFP's without any Origins or Wolverines in between to get what they other wise would from a pay day.
Origins was a box office winner.
The Wolverine was the series' best international take upon its release.
First Class did just fine, and revived the brand in a big way. Also, the
X-Men films are twice as old as the MCU, and less dependent upon the fickle whims of major stars; by that metric, they're doing just fine. How well do you think the
Captain America films will be doing eight years from now?
And even if Disney
did offer Fox enough dough to make a sale financially sensible for the former's bottom line, studio execs thrive on, and aim to make, successful
movies. Even if Fox's owners at News Corp didn't gobble up most of the payout (and why
wouldn't evil old Rupert?), anyone who made that deal with the
X-series in its current state would probably find Hollywood a damned lonely place, seeing as they would've put significant players at their own studio out of sure-thing jobs. And if they decided to try to move to another studio, and escape the glares of everyone at their office, who'd want to hire them after
that show of loyalty?