All the articles are pointing out is the pro rata clause. The Big 12 can add as many schools as they want and the television networks would have to pay each additional school the same amount they're paying current schools. But, if the Big 12 adds a couple schools and the networks are forced to pay the extra amount, those schools better be appealing to the networks or the next go around of negotiations will not be pleasant at all.
Particularly if the Big 12 adds some AAC schools...schools which ESPN currently has in its portfolio for about $10 million per year...and ESPN is now forced to pay them 3 times as much for the next 9 years...