I recently went to a shop and priced out a system for my car. I was shocked when the price to install a $300 head unit turned into $800 with installation, parts, etc. The guy said it was beacuse of my Onstar. I knew i would have to spend more on a unit b/c of Onstar, but $500 for installation. Was he trying to rip me off, or is this common for the newer cars? I have no clue when it comes to audio. Any feedback would be much appreciated.