The more limited something is, the more we desire it. This is a core economic pillar and the basis of supply and demand. If the demand for a product stays the same and supply decreases, the price increases.
This economic application is just one example of how scarcity can be applied in the marketing world. There are four primary ways to incorporate scarcity into your marketing and products: time, money, exclusivity, and availability.
Limited time offers are one way to incorporate time and money scarcity into your promotions (this is a tried-and-true strategy of direct response marketing). Limited edition versions of products are one way of fostering scarcity in availability, and VIP clubs are using scarcity of access (exclusivity) as a way to boost membership.