The money will be big. But I don't think ESPN, Fox, etc. are interested in investing BILLIONS on regional football. Maybe if they see it as a path to national interest, but not over the long-haul.
The SEC carries a big stick, so I gotta believe creating an SEC playoff and having writers throw out $100M annual payments/school is to make USC, Oregon, FSU, Clemson realize what they are missing out on. Jump on board or get left behind. IMO the SEC adding OU and Texas is just a bridge to adding Pac12 teams.
Just having teams from around the country does not make for a national audience. If you alienate fans of the schools left out, they're not suddenly going to cheer for one of the big schools. They'll lose interest in the sport and realize that there's no longer a reason to fork over money for that cable/streaming subscription. It's very short sighted to maximize profits now and not give a **** about what it'll do to your product down the road. But, that's the American way now so I fully expect that's what they'll do.