As I posted earlier, I really think it's as simple as this ... I am not claiming to know how exactly the powers-that-be calculate exactly what a school brings to the Big Ten financially (I am sure a school's academics is financially additive in some way, getting BTN into a new market isn't AS important anymore but is still a chunk of money, there is probably some type of NPV given to a school's "potential" like the ratings a good Illini team could draw in Chicago, etc.). However, I think it is very clear that no school is getting added with full shares if that school does not increase EACH school's share.
In the example given earlier, if the Big Ten "pot" is $14 million and we each get $1 million at the end of the year, Oregon HAS to bring in an additional $1.1 million for the existing members to support it. And, even though those numbers are made up for illustrative purposes, there are not that many schools that "move the needle" in this sense. I do not know if Oregon does, but I am inclined to believe the list consists of just a handful of targets, and the only one I would be sure about (that isn't in the Big Ten, SEC or headed to either one soon) is Notre Dame.