It is not a guess to read that the Big 10 TV contract says they get paid more in states that they are in than not.
It is not a guess to note that the Big10 has zero interest in adding Pitt and "locking down" a big state like Pennsylvania. Or that there is no support for poaching Iowa State and locking down Iowa.
Every candidate was from a state already not represented and only one per state was ever discussed seriously.
(Notre Dame is always going to be an exception with their national prestige. If you want to argue Clemson is like that go ahead.)
Pac 10 expansion did the same thing. Two schools from separate not-represented states.
1) Again you are talking about eyeballs. Not geography.
2) I don't think we can say they have zero interest in locking down Pitt. I have no idea. I doubt there is too much interest in locking down Iowa State because their team stinks and they don't have fans. Pitt at least has a decent team and some fans. Is it a Notre Dame? No, but I think where the discussion is heading is it worth adding a team like Pitt as team #15 and a team like Cincy as team #16 (even though under y'alls "geographic" argument they still have Ohio and Penn "locked up").
3) The "prestige" argument is close to talking about eyeballs, but you just don't realize it (there are certainly other elements to prestige, but a lot of it is drawing interest from TV watchers). ND is king because it draws a huge number of viewers. Clemson definitely has appeal, particularly in the southeast.
The reason the "prestige" argument doesn't cover all situations is that a school doesn't have to be prestigious to bring something to the table. Take Cincinnati for example - they aren't nearly as prestigious as Ohio State but their lack of prestige and location in Ohio wouldn't necessarily keep the Big Ten from looking at them - rather, it would be a general lack of interest (i.e. eyeballs) in their football team, coupled with the fact I don't think Cincy is the type of academic school the Big 10 is interested in.
4) The SEC is supposedly looking into FSU, but they already have a Florida.
5) It's a pretty shallow and misleading analysis to say that Big 10 and Pac 10/12 candidates for expansion were from unrepresented states. There are an incredibly few number of states with more than one major college. The major states of those teams are typically in the same conferences. In other words, the "candidates" for expansion within states currently in that conference are going to be lesser candidates simply by virtue of being overshadowed in another state.
A couple examples:
Let's go with Oregon. They are a big enough state to support two major colleges: Oregon and OSU. You point to the fact the Pac 12 didn't look to Oregon as somehow being evidence that the Pac 10 wanted to expand beyond its existing borders. To the contrary, the reason they didn't look to Oregon is because there were no decent candidates in the state who were not already in the Pac 12. Were they going to add the University of Portland or Portland State over Colorado or Utah? Of course not.
Look at the schools in the other remaining states (Washington, California, and Arizona). Again, it's about adding the best schools, not about adding new states. The other schools in Wash, California, and Arizona are simply not on the same level as Colorado and Utah:
California
Cal Polytech State
California State (multiple)
Fresno State
Long Beach State
Loyola
Pacific
Pepperdine
Sacramento
Saint Mary's
San Diego
San Diego St.
San Francisco
San Jose State
Santa Clara
U Cal (multiple, Davis, Irvine, Riverside, Santa Barbara)
Arizona
Northern Arizona
Washington
Eastern Washington
Gonzaga
Seattle
Same thing for the Big 10. DePaul, Northern Illinois, Southern Illinois, or Nebraska? Which one would you like to add?
How about Ball State, Butler, Indiana State, IUPUI, Valparaiso, or Nebraska?
What we are talking about here are teams like Clemson and FSU who, although there is another team in the same state, those are major schools that draw a lot of interest.