Personally speaking, I don't whine about the cost of jobs done by decent mechanics, although I do ask what it's liable to cost up front, and I'll happily point out that if cost is > €threshold, it's not worth it / I can't afford it. That's not taking the piss, and not "you must do it at under this price", more "if you can't do it under this price, fair enough, but I can't afford to do it if it's more"
I do most of my bicycle work myself, and almost all of my car and motorcycle servicing. However, there are times where I either don't have the tools, or the time, or the inclination, to do it myself - at which point it's happily off to the local specialist.
Case in point was #1 son's bike, which was having some trouble shifting on the rings. Couldn't nail the problem myself, and I'm pretty good with derailleur adjustments. Took it down to mechanic at LBS, he nailed it in 15 seconds flat, gave me a "short term" fix and charged me next to nothing anyway on the grounds that I give him loads of free advertising and always buy bits from him even if I'm doing the job myself.
It's a two way street. The mechanic has a duty to do good work without financially raping the customer, the customer, quite simply, has to "not be an arsehole".