We evaluated problem behavior exhibited by 6 individuals with developmental disabilities using the behavioral economic conceptualization of unit price. Descriptive observations were conducted during interactions between the participants and their primary care providers in a clinical laboratory, the participants' homes, or school. Data were recorded on potential reinforcers and problem behavior. After identifying reinforcers for each participant's problem behavior by way of functional analysis, the descriptive data were analyzed retrospectively, using the cost-benefit ratio described by the concept of unit price. Results showed that demand was elastic and produced monotonic response output curves. The results represent an extension of the concept of unit price to severe problem behavior under naturally occurring environmental conditions. (Contains 1 table, 2 figures and 1 footnote.)