The earliest collectibles were included as incentives with other products, such as cigarette cards in packs of cigarettes. Popular items developed a secondary market and sometimes became the subject of "collectible crazes". Eventually many collectible items came to be sold separately, instead of being used as marketing tools to increase the appeal of other products.
To encourage collecting, manufacturers often create an entire series of a given collectible, with each item differentiated in some fashion. Examples include sports cards depicting individual players, or different designs of beanie baby. Enthusiasts will often try to assemble a complete set of the available variations.
The early versions of a product, manufactured in smaller quantities before its popularity as a collectible developed, sometimes command exorbitant premiums on the secondary market. In a mature market, collectibles rarely prove to be a spectacular investment.