They ask you to call them because a shell from ARE may be different than one from Leer or Century, and depending on whether you want one with windows, aluminum or fiberglass, side opening windows or sliders, front slider, or solid glass, or none at all in front, can change the price by hundreds of dollars.
I've got a Leer on my 2010, but I can't give you a price, because it was on the truck when I bought it used. I can tell you that when I bought my '96 RCSB new, I wanted a fiberglass top, color matched to the truck, but at a $1000, it was out of my budget, that was back in '96. I settled for a Century aluminum cap, with sliding side and front windows, for $300 installed.
Personally, I think Leer has the best fitting fiberglass cap for a Dodge truck, but looking at Ludville1's cap above, that ARE doesn't look bad either. The roofline of the cap matches the roofline of the truck as good as the Leer.