Actually, copyrights are free. Registering them however costs money. The law states that the creator of a visual art is the holder of the copyright unless created for some one else, in which case they own the rights once the deal is completed. The reason behind registering is so that if some one steals your artwork you can more easily win the case in court, but it is not required. So transfering a copyright is free, if you decide to give it away free. Once some one purchases a unique design as stated in your deal, he then holds the rights to publish it.
At least that is what I gathered after reading it over a while ago, I could be wrong .