The other thing the B12 offers is long term stability. It's not going to pay them the most money but the schools know where they stand. None of it's members are targets for the SEC or B1G (some may think Kansas is a B1G target but I don't) so they are what they are. Depending on how things shake out with the PAC they may even get to expand.I don't see any way a Big 12 team leaves for the ACC -- right now. If something were to happen to the ACC TV deal to disrupt it, possibly, but what's the incentive for ESPN to do that? They have the ACC long-term = 9 more years for a bargain. Big 12 has momentum. The two leaving teams haven't played in the Big 12 football championship in the last two years. They will have had teams in the 4-team playoffs in back to back years (Cincinnati + TCU) -- with zero appearances for the ACC.
The Big 12 has back to back national championships in basketball and are adding Houston and Cincinnati. Their TV expires well before the ACCs so they can re-up again. They've had really solid ratings on non-Texlahoma teams. TV rights values are close to a wash.
While the new B12 contract is only for 6 years, it is based on the current conference makeup. The ACC contract runs for another 13 years but it's likely that half it's members have at least 1 foot out the door and would be gone in seconds if not for the GOR. And, as you said, the TV money is basically the same.
When the smoke clears (and it may not be until the ACC GOR expires) the B12 will likely be the 3rd best conference after the SEC & B1G. Who knows what the ACC will look like.