my carbon fiber was about $500, i have 5 or 6 usgi fiberglnass stocks and an sai polymer, my carbon fiber is noticeably lighter then the fiberglass and extremely stiff, it is my favorite so far but i haven't shot it yet so we shall see.
My carbon fiber was around five hundred as well. It was a very nice stock. The lightest i have ever come across. Very stiff, but for me personally it did not feel much stiffer than my reinforced fiberglass. It definitely was more stiff but i couldn't feel any difference and my rifle shot better in a usgi fiberglass. I ended up trading it to m1army for a stellar fiberglass stock, with a sadlak hd rail that has the sling swivel and qd stud. Plus he nm'ed the front, custom painted it, and reinforced it. It is currently on my wolfe dmr and i feel really good about the trade.
I did really like the the lightness of the polymer and got decent results from it but the carbon fiber is awesome.