The only thing is, with Bitcoin we have the numbers. The classic banking system look like a few thousend banks with thousends of buildings with hundreds of thousend computers and million of emloyees. The employees again need to eat, sleep, drive around. They have money that needs to be designed, to be printed, to be distributed. All this cost ressources too, but this really hard to put in numbers.
Bitcoin has the energy consumption of small nations. Banking is one of the many things that can be self contained in the energy budget of a small nation. On the other hand, bitcoin's transaction throughput would constrain my neighborhood's commerce at lunch. That is to say, traditional banks are doing a whole lot more to facilitate actual commerce.
It would seem to me that the efficiency gap is insurmountably large.