If your trailer is back-up camera ready (on the back of the trailer there will be a mounting bracket and the trailer is pre-wired to power the camera) then the $649 is about $300 higher then the cost on Amazon. If it's back-up camera ready the installation is very easy.
If they have to install a mounting bracket and tap into the trailer wiring to make the trailer camera ready, and you don't want to mess with cutting into your new trailer to do this yourself, then the $649 seems reasonable IMHO.