We had a problem with our Nissan Xterra truck. It started strutting badly at around 3k rpm when accelerating to ~40 mph. We brought it to a Sunoco service station at intersection of Route 123 and Gosnell Rd in Vienna, VA. They faxed me an estimate with a quote for $560 (including the diagnostics) for tune up, which is spark plugs, wire, rotor cap etc. I agreed. Next day, they called me and said that there's an issue. They have to also replace the mass air flow sensor. I asked the new price and it was $600(!) more. When I spoke with a mechanic his explanation was that if he gave me the quote for $1,200 then I wouldn't leave my car in his place, that's why he quoted me only the half the price! That was the most ridiculous excuse I ever heard.
I spoke with the manager, and he maintained the similar story, that they had to start with simple things first. Well, what about $90 for diagnostics?! I said I don't care and simply want my car fixed for the quoted price or get it back. After some argument with the owner I got my car back presumably in the original state + oil change.
Next, I brought my truck to Nissan dealership. Their quote was $850 to replace MAF + some other work recommended, total to $1,800. I spoke with a couple of friends who fix cars, and they both recommended me to replace MAF on my own. So, I bought the used one with one year warranty in Advanced Auto Parts online for $140, shipped free in 3 days. When I opened the trunk, I started laughing. This damned MAF is the first thing you notice under the hood! It's probably the easiest part to replace in whole car! It's fixed with two screws. I also changed the air filter, $10. All in all it cost me approximately 150$ + one hour work (including the test drive).