You're kidding about all this, right? Please tell me you're kidding, because I know you're smarter than this.
OF COURSE not every addition of a school adds money!!! That's why nobody is racing to add UL-Monroe! The point here is that there is most certainly an "arms race" going on here, and it is involving well known universities, tv markets, etc. Is there anything that inherently makes Missouri an SEC team? Is there anything that inherently makes WVU a Big12 team? How about Louisville becoming a member of an "Atlantic" Coast Conference? (all these questions were rhetorical, so I'll supply the "no" for you). They were deemed to be additions that would add monetary value to the conference, or at the very least, membership stability (which is monetary value also).
And if you think that each major conference isn't actively continuing that process, in order to insure their respective long-term survival (a.k.a., don't "Big East" yourself), then you are kidding yourself and others...