Well the factory decal is clearly priced to increase the margin on the vehicle while permitting them to claim a lower MSRP. As far as I could tell, the price they chose is driven by the usual markup of vinyl from a local installer plus installation costs. Could they deliver a reasonable product at that price? Yes, but they would have to ship a lot of stuff and control the costs on the install kit. Have they? No idea. I can say that I doubt the pictures in the ad are of an actual application given that most trailhawks showed up with decals and they are pictures from dealer lots.
Alphavinyl does seem to move a lot of decals though, and you can read through their amazon web shop for reviews: