Some dealerships use the TSB's as a way to make a quick buck without much thought, too. I had a 1985 Ford LTD LX many years ago, and it had an idle speed problem. Whenever it warmed up, the idle became very erratic, and would go up and down between 500-1000 rpm at idle. The dealership took one look at it, checked their TSB's, and decided it needed some new circuit based on what the TSB's said. $350 later, it didn't change it at all. I took it back, and they put it back in the shop while I waited. They came back with some other sensor, and the service manager said (exact quote) "we think it's this now". I told him if he couldn't tell me what it was, with all their electronic tests and expensive mechanics, then put it back the way it was and I would live with it. I can change parts with the best of them, but a true mechanic can diagnose the problem and fix it the first time.
I bought that sensor from another dealer ($35 instead of the $60 they quoted me!) and it didn't fix it either. It took a local mechanic who was irritated that he couldn't figure it out to find an obscure temp. sensor buried in the heater hose.
The dealership was Tommy Vaughn Ford in Houston. Great sales dept. and Ford Motorsports parts, but truly lousy service dept.
TSB's are not free if out of the warranty. And they may not even fix the problem.