Had a similar experience in the late 90's when I was working at Radio Shack and I built custom computers out of parts in the store. At first I would put together the items then price them out to the customer. When it was done of course the customer would complain about the price. The owner of the store had me make a sign of everything I did, repaired, reformatted reinstalled, parts, etc. When I would get a question, I would refer them to the sign. As the owner said, if you have your prices posted they can't argue with your posted sign.
Also on a similar note, it's crazy how people perceive computer work. I'm doing less of it all the time due to poor "good nature" of customers. If you do an install of Windows and all their programs, make sure their AV is working, for $100 they cry bloody murder. But if they take their car to a mechanic and he says $500 they don't bat an eyebrow. Probably similar in the equipment repair industry. Sheesh...