Artificial scarcity is a method used to inflate the value of something by only creating a limited amount. Modern manufacturing techniques make it relatively cheap and easy to create vast numbers of the same
magic card,
lead miniature,
action figure or
beanie baby. However creating enough of an item to satisfy the demand for it is not desirable if a company wishes to create a lucrative collectible market and/or
gouge the hell out of it's customers.
In some cases (Magic cards for instance) people will purchase large quantities of things they don't want simply for the chance of getting something they do want. In other cases companies appeal to the fact that there are people who will collect anything. In still other cases there is a monopoly (legal, illegal, government regulated or otherwise) which prevents bothersome competition and allows a company to basically do whatever the hell it wants with regards to availability, prices and quality of service.