Who does that money go to? The Big 12? if so, what do they do with the money? Especially when they're dissolving next year.
The money goes to the B12 who is going to distribute it to the remaining members (those that were in the league prior to TX and OK announcing their departures).
The B12 is not dissolving. They signed new media contracts and the GOR remains in effect.
The key was Texas and OK were waiting until the current media contract expired to leave so that there was no value they were giving that they would have to negotiate over. Just to leave 1 year early cost them $50M due to the GoR. That wasn't an exit fee, it was a negotiated settlement of leaving with 1 yr remaining in the TV contract and being able to leave and retain their media rights so the SEC could broadcast their games and make money.
Now that the B12 has a new media contract it would be extremely expensive for any school in that conference to try to depart (just like it would be in the ACC).
How analysts are arriving at numbers like the $500M number to leave the ACC are pretty simple. If a program was to leave the ACC right now the ACC would retain their media rights for the next 13 years. So over that time period the program (and more importantly, the new conference) would get $0 for their media content. It would all simply go to the ACC. Say the media rights are worth $30M yr per program. Simply multiply that number by 13 and then add the current Exit fee $120M and you get over $500M that the ACC could say a program would owe if it wanted to leave the conference and have control over its media rights and make the conference whole.
Note that both the B1G and SEC have purposely waited until media contracts were expiring in the conferences that they added teams from. That is hardly a coincidence.