OBJECTIVES: 1) To examine the practice of calculating a sample mean cost for each of two or more cohorts, reporting the difference(s) as the incremental cost(s), and reconciling this practice against the common assumption that the underlying expenditures follow a two-parameter gamma distribution, and 2) To revisit the interpretation of incremental costs based on the difference in sample means as the properties of the assumed underlying gamma distribution vary. METHODS: Monte Carlo gamma distribution simulation in SAS version 9.3 varying the shape and scale parameters for the simulations and displaying the results in graphical and tabular format. RESULTS: It is possible to create examples of simulated data sets where the sample means have values that can be in excess of the estimated 75thpercentile.   CONCLUSIONS: An analyst should be cautious in his or her reporting of incremental costs as the lay consumer of these quantities may interpret the difference in the means like they would for two or more somewhat symmetrical distributions where the mean can represent the center.  However, this interpretation might be misleading depending on the magnitude of the shape and scale parameters that characterize an underlying distribution's behavior.