Two more things to add about banks, one is that other people will be depositing money. This means you could rob the shopkeeper while he's on the way to the bank. The other is that the shopkeepers can have some money to buy your stuff in the store, but keep most of his money at the bank. One or two robberies won't put him out of business this way, and if you wanted to sell him an expensive item, he could get the extra money from his bank to buy it from you so you don't have to take a huge loss on it. The bank will be the means for you to be able to sell your high end gear to shopkeepers.