Fundamental differences between the optimization strategies for power cycles used in "traditional" and solar-thermal power plants are identified using principles of finite-time thermodynamics. Optimal operating efficiencies for the power cycles in traditional and solar-thermal power plants are derived. In solar-thermal power plants, the added capital cost of a collector field shifts the optimum power cycle operating point to a higher-cycle efficiency when compared to a traditional plant. A model and method for optimizing the thermoeconomic performance of solar-thermal power plants based on the finite-time analysis is presented. The method is demonstrated by optimizing an existing organic Rankine cycle design for use with solar-thermal input. The net investment ratio (capital cost to net power) is improved by 17%, indicating the presence of opportunities for further optimization in some current solar-thermal designs.