I love how people jump to conclusions that the dealer is ripping them off, based on the word of a "trusted" mechanic. It doesn't take much effort to use the resources at a hand such as this forum or better yet call the the dealer and get the price from them. I've been in the business over ten years, and I do have people calling all the time to check on parts price, but then again I'm in the northeast and we're not too trusting up here.
The problem is that people assume the mechanic thay take their car to is knowledgeable. Trust me, the majority are not. If you do find a good one, grab hold for dear life, because they are worth their weight in gold, because they are a rare commodity.
If only people could hear some of the conversations we have, its like a comedy sometimes. Here's an example, last week we had a shop call for an "intake exhaust"!!! Sometimes the mechanics ask for the wrong part or don't even know what to ask for.
Best advice is use your resources. We live in the Information Age.