I read in multiple areas it was $25m. But that's fine, was probably settled at $15m or something.
Regardless, Kentucky should be able to find the money or at least get Cal to negotiate. I know people here think Cal is some wacked clown that will go down swinging and taking Kentucky basketball with him to get that money, and all of it, but I don't agree. I want him gone and think he's definitely an egomaniac, but his core focus is that if he has to go and is forced, he will want to go in a way that doesn't leave the entire media world calling him an arrogant greedy ******* for the rest of sports history. He'll want to try to leave whatever legacy he has left in tact and go off being seen as as a compromiser, not an asshat.
I think $15-20m would do it. Cal might put up a small fight internally with making propositions to convince certain kids to return, have a complete staff overhaul, and make hollow promises to coach better, but ultimately I think those ready to pay up are fed up and don't believe a word he says. He's had his chances and still flopped. One more year with the same talent isn't going to change the outcome.