A modular simulation code, CAMEL (TM), developed by the University of Romal, has been adapted to include the capability to perform a thermoeconomic analysis of a MSF desalination plant. The existing tool already calculates the exergy losses in each component, and it is endowed with an economic cost utility that makes it a very useful tool in optimising the allocation of energy resources and minimising the product monetary cost. Since the MSF process requires low-temperature steam, it is usually deployed as the bottoming part of a combined power plant. The combined cycle has been also simulated and its thermoeconomic analysis has been performed in order to determine the cost of its products (steam and electricity). A model for the thermoeconomic analysis of a MSF stage has been developed and the results have been compared with existing literature data. Before proceeding with the thermoeconomic analysis, an exergy analysis was performed, to allocate the inefficiencies across the MSF stages. Different MSF plant configurations have been coupled with the same power plant: all of them have the same total heat exchange surface, but they differ as for the number of stages (18, 24, 30 respectively). The distillate cost has been derived and the optimal configuration and operating conditions have been determined. The results show that capital-and steam costs are equally important in determining the optimal operative conditions. For the present analysis, the 24 stages configuration, even if characterized by a sub-optimal efficiency, results to be the most convenient.