commodity theory
a theory proposing that the value of a product or service is related to its availability. In general, a product that is in short supply is perceived as having greater value than one that is readily available. However, a product’s value is also related to the demand for it. It may be scarce, but if no one wants it, it will not have a high value. Commodity theory is used to explain consumer behavior in times of product or service restriction. [formulated in 1968 by Timothy C. Brock]