AI don't buy much at shops except dash kits or emergency RCA's and wire that's about it, we do have one local dealer I buy stuff from because he is a good dude and he knows what he is doing (he is a dealer not a shop that does installs but he could do Installs if he wanted). But shops have to charge that much guys. They have to pay rent on their building, pay for everything that sits in their shop, display cases, demo vehicles in some cases, employee salary, taxes, Ect.
Yes, you can get better for less if you can install yourself or know guys that can. But, to the average person that is not an Internet geek on car audio forums (like us), they just want to have a good stereo, and don't want to spend all their time researching, making an account online, ordering used stuff from random people. They just want to drop a paycheck, and have instant gratification.
I think you guys are a little closed minded, think about this... When MOST of you guys want to have a new roof put on your house.... Do you go on roofers forums and research how to replace it TO CODE by yourself? Then go and rent all the equipment you need and have you and your friends replace your roof? Maybe 1% of you. So keep that in mind.