It's not unlike the car repair business (which I'm in).
Some people are grateful when you find a number of faults on their machine and will be happy to authorise and pay for the work. Others will assume you're trying to rip them off and will post poor reviews on internet forums. (I'm not referring to the OP here, it's a general observation)
It comes down to integrity at the end of the day.
If the company has integrity they will always find as much wrong with your machine as they can and then offer you information such that you can make the correct decision on whether to proceed with that work or not.
Is it a safety issue?
Is it a legal issue?
Is it a reliability issue?
Is it a cosmetic issue?
Is it a performance issue?
Is it an issue for the re-sale value?
These discussions get easier once you have established a relationship with your repair organisation because they originate from a position of mutual trust.
What you should never do is assume that the cheapest is the best!