Even without the pro rata clause, the Big 12 could have added 2 new schools and pointed to the increase in 10+ games of inventory to get more than $10M per year, even after the new members took their "haircuts."
Concurrently, the Big 12 would have dealt with the "psychological disadvantage" and would have avoided the silly round-robin plus CCG setup that they will implement next year. You know, the system that could see 8-4 Oklahoma beat 12-0 Baylor/WVU in the CCG and ruin the conference's chances at the CFP.