Just because the SEC has a national contract with ESPN does not mean that it will not get added value, beyond the number of fans for a school, from having a member in a new distinct location, Texas, for example. There are Jefferson-Pilot level SEC games as well. Those games would be available in Texas if there were an SEC member here. As it is, we only see those national SEC games. But I get lots of Big Twleve games on broadcast TV that you would only see with PPV.
The Big Ten Network contract should make the value of having a footprint in a state plain. They get paid considerably more by contract in states where there is a Big Ten school. But what is rleevant is that there is a reason they are paid more. That reason is that it is worth more in both advertising value and package value to consumers.
It is not the ONLY consideration for choosing an expansion target, but I assure you it is something that they have evaluated in cost/benefit analysis.