Business, and car repair business
I am impressed by the level of expertise exhibited on this site, I am new (3 days) to this site and can't get enough.
This, to me, is the typical case of "it's not what you do, but how you do it" A mechanic or shop is no different than any other business, looking for a mutually beneficial relationship. I find, unfortunately, few take the long term approach of a happy customer is a returning and therefore profitable customer. I will drive 30 miles out of my way to get my parts from a Mercedes Dealership who speaks to me politely and who's mechanics treat me with courtesy and respect.
I have always been willling give something "profit margin" if I get something "customer satisfaction".
I find little value in nickle and diming people in negotiations, a deal must have two winners to be a deal.
Be prepaired to give a little to get a little and use common sense.
I believe a mechanic or shop is no different than any other business partner. Good ones are hard to find and you are willing to pay a little extra to preserve that relationship.