All right, most of the defenses for the mechanics are good. And there're many honest mechanics are out there. But let me ask you a question. What if the mechanic knows exactly the problem can be repaired for let's say $500; however, he went on and charged $1500 for other problems that need not to be fixed? Also, what if the total time he spent on fixing the problems is only 4 hours, he charges 10 hours for the job, given other shops do it for 10 hours?
Conclusion: I strongly believe the above cases are all "Rip-off". Only unethical mechanics do this. It's not smart or whatever. Those mechanics gotta know people sweat to earn the money to pay for repair; of course that those mechanics sweat, too. But an honest and ethical mechanic or any other professional only charges for his truth work, and not cheat their customers. He can raise his charge based on hour or product, but not to cheat the unearned or unneccessary works. If the customer agrees to pay those charges with his high quality work, otherwise, the customer can have options. This is real honest mechanic with real quality.
I've been there and done that. I also have relatives as mechanics. And myself is a current non-licensed mechanic but used to work on cars for people part-time when I had several certificates. I'm not strange with honest and unhonest mechanics so the best thing that I'd do is to shop around and have a receipt when the job is done. Also, talk to the mechanic first to see if he really knows about car or he's just bluffing about general things.