Did you go to LA Tint in Sterling? I didn't think/know he had another shop out there, only in Alexandria. That price sounds more in line with LA as they run a little more.
I forgot to check the brand, but it's charcoal and he carries a lifetime guarantee. I have no experience with getting tint at a dealership, so I can't really comment on the quality or price. But I would assume, like everything, they'll charge you more at the dealership (unless you're K and have a hook up). May be worth it to ask? I know Matt at TNT has been in the area for several years and has done tints for most of the law enforcement agencies and athletes around VA/DC, and has a very good reputation in the area.