They are right in one sense and egregiously wrong in the other.
Bankers spend their income just like all other businessmen.
Bankers are not suppliers of tangible goods and services subject to the law of supply and demand, however, like the price of strawberries down at the corner fruit stand. In this respect banking is analogous to the services provided at the county court house. Any written contract can be filed or recorded there. To be enforceable certain contracts are required to be filed there. The upper limit to the fees the court house charges for this service is not determined by supply and demand in a free market.