Exit penalties are a fool's game.

#1. Anyone who thinks they might have something new and shiny coming their way, won't support the exit penalty being any larger than what they think the new and shiny is worth.
#2. In many jurisdictions statute or case law provides that association or partnership departure penalties cannot be so high that it is punative in nature and must bear some relation to the damage done. If Big East signs the mega TV deal they claim to expect, what damages are being done by the schools departing? They are ponying up because they don't want to hang around to see what the actual damages are.
#3. Since the exit penalty can't be high enough to keep anyone from leaving, the penalty serves no purpose.