I thought about it and thought why didnt they try to scam him when selling materials or buying clothes then it hit me, he said his father wanted to sell the materials, then the shop owner would have thought that the father knew the price and if he screwed him over he would get a sword to the throat, since these are pretty powerful critters. Same but different story goes for OH BOYS he on the other hand probably thought that the child, since he had a large pool of wealth as a merchant he would get on good terms and was rewarded.