Not car related, but I recently bought a Panasonic Plasma screen and Blu-ray player.
I went to a Panasonic dealer to get all the info on it, knowing they woud be the most expensive but would give most information, then went to Currys, House of Fraser, Ebay, RIcher Sounds, various online discount AV dealers, to see who was giving the best deal.
To my surprise, the main Panasonic dealer was £100 cheaper than any of the others for the hardware, plus they included a 5 year manufacturers warranty, free HDMI cable, free delivery and free technical setup by an engineer. The others wanted an extra £250+ for the additional stuff.
Again, it looks as if "main dealers" can be better value than some think.