You say that in one year, a new Pac 12 conference tv contract with some number of Big 12 remnants would cover the exit fees from the Big 12 departure.
First, you argue it's $18M per team. That could be true, but $76M is the amount a team has to pay to leave. So not only does each team lose access to the Texas/OU revenue (let's assume that's $18M each), it also has to pay $76M. That's a total hit of $94M.
Second, you argue that if it was an $18M hit (and it's a lot more in reality), they could make that up in one year with additional tv revenue.
The latest figures I've seen are that the Pac-12 gets about $310M in tv revenue annually to share among all members. That breaks down to about $25.8M per team. To make up an $18M loss in one year, the Pac 12 would have to generate an additional $18M in revenue per team in the conference. Let's say they add just two teams of the Big 12 remnants. The new Pac 12 would have to then be worth $613M per year (doubling its value). Do you really believe that any of the Big 12 remnants are worth an additional $300M in Pac 12 revenue annually? Which ones? If they are, you're right- they will be gone in a heartbeat (to the NFC West).
If the Pac 12 were to add four of the Big 12 remnants, the Pac 12 would have to make $700M annually, meaning the four new teams in the aggregate would have to be worth $100M per team. If they add 6, the Pac 12 needs $785M, so the six need to be worth about $80M annually per team. If they add all 8, the Pac 12 needs to get $872M from its tv contract annually, so each team would have to be worth an incremental $70M annually. As an aside, the Pac-12 with the Big 12 remnants would then be getting a larger tv contract than the entire SEC receives annually.
Does that seem likely to you? Seems a bit... unrealistic to me. And that's just to cover the $18M in lost revenue from TX/OU. The numbers are astronomical to cover a $76M departure fee.