I would say that it is the service writers more than the mechanics that try to screw you
The last place I worked at as an inspection mechanic had a blanket policy (verbal, of course, from the service writer) which stated that every car that came into a bay had SOMETHING wrong with it, even if it was just wipers.
One of my grandparents friends came in for an oil change one time, but I was off that day. They charged her $35 for an oil change and another $30 to change a turn signal light. Unbelievable! The worst part is that the love muffin mechanic (who was the service writer's brother) left the oil filler cap off when he was finished. I almost felt like telling her to run it dry of oil til it seized and sue them over it.
There was another time that a friend of the service writer had come in for an inspection and his rotors were way under spec. Almost .015" or something ridiculous like that. The service writer told me to put a sticker on it anyway. I flat out refused and told him to put his license in jeopardy, and that he should sign off on it if it was so important. It would be MY bellybutton in a sling if his buddy's brakes failed and he hurt someone because of it. He said he couldn't because his inspection license was issued in N.J. and, if I didn't do it, he was going to make my life "very difficult" I told him to blow it out of his bellybutton and that I would make his life simple for him. I quit immediately with a garage full of cars, two of which I had on a lift, in various states of disrepair.
It is usually the family owned shop with a full parking lot (usually meaning he is popular and does good work) with an owner that will come out with smile, a greasy handshake and dirty coveralls to shake your hand, being the shop you can trust.