This paper combines expressions for infant formula retail price flexibilities of the contract brand with respect to the rebate and participant demand presented by Reed and Levedahl (2012)with historical data on rebates and participant demand to calculate how the magnitude of net taxpayer costs has been affected by changes in rebates and participant demand. These results are used to compare the relative impact of these variables on the net cost to taxpayers of WIC infant formula and to evaluate how effective sole-source contracts have been at containing taxpayer costs.