Materials costs are an important theme in contemporary thermoelectrics research, for example as a critique of sophisticated nanostructuring for high ZT, or as a motivation for polymers of moderate ZT and very low cost. Here we consider the cost-performance optimization of an energy scavenging system (free heat), accounting for the costs of the material, manufacturing, and heat exchangers [1,2]. The analytical treatment  couples the economic, thermal, and electrical problems to minimize the system-level cost per watt, which can be related to an equivalent levelized cost of electricity (LCOE). This analysis builds on prior works which considered the materials cost alone , used a simplified manufacturing cost , had one-way coupling from thermoelectric performance to cost , or were purely numerical . We considered realistic cost and property values for 30 bulk and thin film materials, as well as manufacturing and heat exchanger costs . For the large majority of materials we find that the total cost of the $/W optimized system is dominated by the heat exchangers. In this regime we obtain simple expressions for the optimal leg length and fill factor, compatible with realistic contact resistances and other parasitics, and below which there is little additional reduction in the system $/W. The materials goal in this most common regime may be summarized as the pursuit of “high ZT at any cost,” at least up until materials costs of ~$100/cm3.  S. K. Yee et al., Energy & Environmental Science 6, 2561 (2013).  S. LeBlanc et al., Renewable & Sustainable Energy Reviews 32, 313 (2014).  G. G. Yadav et al., Nanoscale 3, 3555 (2011).  D. M. Rowe and G. Min, IEE Proc.: Sci. Meas. Technol. 143, 351 (1996).  K. Yazawa and A. Shakouri, Environmental Science & Technology 45, 7548 (2011).  N. R. Kristiansen et al., Journal of Electronic Materials 41, 1024 (2012).