The main purpose of this work is to apply thermoeconomics concepts to a projected steam injected gas turbine cogeneration system, which aims at providing the thermal and electrical demands of an industrial district sited in Cabo (Pernambuco, Brazil). The power plant is evaluated on the basis of the First and Second Laws of Thermodynamics. A thermoeconomic analysis, using the Theory of Exergetic Cost, was performed in order to determine the production costs of electricity and steam. Two hypothetical operational conditions, as regards the level of electric power generation, were considered.