I realize Missouri will have to pay something, but I really don't see why it would need to be some outrageous amount.
The Big XII is only one big happy family in Wickedson's tiny little mind. There are the schools that wanted to leave but couldn't because the Pac-12 wisely came to their senses, the schools nobody else wants, and the castoffs that have no idea what they're getting into. But however dysfunctional they may be, they've moved on, have new members and a full schedule for next year's season.
There are no damages here, beyond KU butthurt, which really doesn't rate any consideration, monetary or otherwise. It's not like Missouri's absense left Big Texas teetering on the brink of ruin.