Oh, Anaris. No matter how upside down weird anything is, you always see it perfectly right side up and normal.
Hey all that food you have in your fridge, I'm going to take it and sell it all and give you none of the proceeds. Perfectly normal. 
Why do we keep having the same conversation over and over about this? The banker access is optional. If you don't like him poking around your granaries, don't let him. If you want him to do the trading but still earn some gold, come to an arrangement with your banker in order to do so.
Middlemen throughout history have made their money facilitating deals. Often they do so without having to worry about logistics or warehousing, they just have the contacts,skill, knowledge to set up need A with supply B. So it is with the Bankers of Battlemaster.
