You've been reading UT propaganda. The Big 12 by-laws provide that the Big 12 will begin to withhold conference distribution payments immediately from UT and OU - they're about $40 million per year, and for 4 years, that'll be about $160 million. Each. ESPN, Fox, the Sugar Bowl, the NCAA (for hoops credits) and others will be paying that money directly to the Big 12 and UT won't see any of that. Ever.
If UT wants out early, it'll be a lot more and they will cut additional checks made payable to the Big 12. (Of course, it's all subject to settlement negotiations, and if otherwise agreed, it could be an agreed amount). UT is under the delusion that the exit fee is $80 million, but they stupidly noticed 4 years early rather than the required 18-months - that is only beginning to dawn on them. Further, they have this delusional assumption that a "discount" is "always" applied - that is not accurate. TCU paid the full Big East exit fee ($5 million) and other schools have done so as well. Discounts apply when there are other mitigating factors (not present here) and the Withdrawing School hasn't blatantly breached a 99-year commitment, a 12-hour notice provision and a requirement that they immediately and firmly reject any offer from another conference.
if UT wants to leave early, the onus is now on them to make us an offer - and it better be well in excess of the $80 million they think they owe.
Until this is resolved, the Big 12 has no interest in pursuing expansion at this time. Moreover, the AAC notice window is 27 months - talk to us again in about 1 year and a half. It would be earlier if and only if UT settles for an agreed amount.