If they do not play, outside of merchandising the school's revenue is zero in 2020. If they play in the Big 12 for instance, the TV revenue and (smallish) ticket revenue might equal or even offset the financial penalty for walking out of the conference. Plus the school considering leaving has to also ponder the possibility that this could be a two year shutdown in the PAC-12 and Big Ten, in which case the money gained from playing in 2020 and 2021 would definitely offset the one-off financial fee for leaving.