To encourage collecting, manufacturers often create an entire series of a given collectable, with each item differentiated in some fashion. Examples include sports cards depicting individual players, or different designs of Beanie Babies. Enthusiasts will often try to assemble a complete set of the available variations.
Early versions of a product, manufactured in smaller quantities before its popularity as a collectable developed, sometimes command exorbitant premiums on the secondary market. Dolls and other toys made during an adult collector's childhood can command such premiums. Unless extremely rare or made as a one-of-a-kind, in a mature market, collectables rarely prove to be a spectacular investment.