Well, "economic sense" isn't as black and white as simply looking at their energy consumption. Banks spur the economy by lending, and they provide jobs, etc, so you're going to have to factor in much more than just cost. The economy is a complex thing.
To answer your question of consumption, here is an article I've read about the subject:
https://hackernoon.com/the-bitcoin-vs-visa-electricity-consumption-fallacy-8cf194987a50tldr; Author conservatively estimated banking's energy costs to be around 3x Bitcoin's
