Jay, I completely understand your complaint, and I honestly feel there's no need to argue it. If they're all using the same book, they should all come up with the same answer, and they don't.

Slightly aside, but slightly to the point, I've been to places that claim I need to change the timing belt on my old Volvo, because if it brakes, it will ruin the motor. When I ask them where they determined that the engine is an interference engine (which, BTW, it isn't), they claim its from some heavenly shop manual that all shops use. This of course was at an independant shop, and therefore not held to BMW or other corporate standards, but my point is that they may have the book, it just sits unused on a dusty shelf while they pull numbers out of their ass.

One other scenario I thought may be contributing to this is that the shop is possibly quoting more sub-jobs than another shop. For example, when you say you need the corner lamps replaced, mabye one shop was able to find a labor estimate for the corner lamps and quoted you for that, while the next shop just assumed that the headlights had to be pulled to install them. They're both quoting from the book, just slightly different jobs to accomplish the same task.

I want to say thanks for taking the time to document your research.