Well this one was free because it was leftover from making some other parts. But a roll of carbon fiber that is 1 yard by 50 inches is anywhere between 30 and 50.00 shipped depending on the manufacture and the weaver of the cloth.
Plus you need to add in some epoxy, Brushes, clear coat sandpaper, rubbing compound, polish, wax, and vacuum mold supplies. It adds up pretty quick. However, if your doing it regularly the costs go down.