$400! Only I would be dumb enough to pay that much.
Actually I paid $260 to get a rear slider (170 for the glass, 90 install)
installed at the dealer where I purcashed the truck.
Truthfully, I got taken. You can get a wonderful 2 glass slider installed for $150. My brother-in-law got a beautiful CR Laurence window for $100 and 50 to install. Or, a solid rear window is available for probably under $75.
The dealership told me my old one would be unusable, since they break when removed. That was pure BS, because I saw the glass guy come out and drop my old window off at the parts counter. I was being nice at the time, and didn't call them on it. That won't happen again. I'm sure they sold that window to someone at cost.
Honestly, go to a few glass places and get pricing. You can get good quality SECURE rear sliders that won't rattle. Ford uses the worst POS sliders on the market. For $400 you can get a powered rear slider
Think of this as a good opportunity to upgrade. :D