Well you can talk TV markets all you want but it's irrelevant if the area doesn't care about the teams. Look at the disaster of the Pac-12 Networks. Are cable providers going to add a Big XII network around Orlando when UCF is second fiddle to the SEC? Orlando is a bigger market than SLC but I'd imagine probably comparable buys when it comes cable providers that would carry the Big XII network in that area.
Also if you've been paying attention, the Big XII is very interested in playoff odds. The bonus from getting a team into the semifinal is $6m and a $4m bonus for every extra team in a NY6 game. Those bonuses are probably more significant than the addition of those TV sets. Adding a team that just went 0-12 (despite endless POTENTIAL) probably isn't the best way to go forward for the league.
And you think the Big XII is safe from breaking up until 2025?
Dude, the Big 12 Network is dead; Boren said so himself. They are going to look into an internet-based network, but ESPN, Fox, etc. won't back a B12 Network because of the financial conditions around cable-cutters. But yeah, if there had been a B12 Network, Bright House would have had it in Orlando and Tampa, not a doubt about it. UCF has a distribution deal with Bright House where some UCF athletic events are shown on Bright House Sports Net.
Though it's not relevant since there's not going to be a B12 Network, your point about the bowl payouts > network payouts isn't accurate. That's $10m, as you say, and the value of Orlando + Tampa in terms of cable subscribers (and because Bright House has both Orlando and Tampa, you don't need both teams), would be $40.1m/year based on # of TV households * $1/month. The SEC Network gets >$1.40 per in-state subscriber, so if we just assume the B12 Network would get $1 and only get it in Orlando and Tampa (and not in South Florida, Ft. Myers-Naples, Jax, Tallahassee, Pensacola, etc.), you're at that $40m figure.
And finally, the Big 12 is looking at playoff odds from the standpoint of whether having a 13th data point helps move a team into the Top 4. They're not nearly as concerned about adding another team that is seen as a quality win for next year. While Top 25 wins are a major factor for the committee, trying to judge that based off of one season or something is silly for expansion purposes. They are looking for a team who has everything in place to be a Top 25 team consistently, and as I said previously, it's doubtful that BYU would be in the Big 12 because they can't recruit at the level to be able to compete at a P5 level every week. Maybe UCF won't be, but there's a much higher chance that UCF could be and could replicate TCU's success.