This movie is designed to be fun, and its intentions are signaled to us over and over again, as when the women jump around on a bed, giggling and flinging old, dirty money around in a wanton display of pure idiocy.
What's not to believe? A lot. But asking for bolted logic and dramatic structure in such a movie is about like asking former Fed chief Alan Greenspan to open a mosh pit in Miami. Anyway, the money in the bank here is Keaton.