Comparative exergo-economic analysis of a simple and modified cycle gas turbine power plants was carried out in this work, using a GE MS5001 gas turbine located at Trans Amadi in Rivers state, Nigeria as a case study. The simple cycle plant was modified to have an intercooler, regenerator and a reheater with one additional compressor and one additional turbine. Energy, exergy and exergo-economic analyses were carried out on both plants. The net output of the GE MS5001 gas turbine is 26.90MW, and its fuel is natural gas with heating value of 50MJ/kg. The simple gas turbine cycle has an efficiency of 30.4% while the modified gas turbine cycle has an output power and efficiency of 44.67MW and 48.0% respectively. The exergy efficiency of the simple cycle is 22.6% while that of the modified cycle is 43.0%. The highest exergy destruction rate was in the combustion chamber in both cycles and accounted for 90% of exergy destroyed in the simple gas turbine cycle and 43% and 36% in the combustion chamber and reheater of the modified cycle plant. The economic analysis carried out showed that the total purchase equipment cost was higher in the simple cycle plant because of the high pressure ratios the compressor and the turbine operate in the simple cycle compared to the modified cycle. The cost of producing electricity for the simple gas turbine cycle was 10.18$/GJ while that for the modified gas turbine cycle was between 7.3339$/GJ and 7.7969$/GJ. The cost of electricity from the modified cycle is thus cheaper. All the exergo-economic parameters favour the operation of the modified cycle.