This paper introduces a comprehensive control co-design (CCD) methodology for optimising the layout of wave energy converter (WEC) arrays from an economic perspective. The CCD approach ensures that all optimised WEC and array parameters are aligned with the final control strategy, resulting in an optimal design from an overall perspective. By integrating a spectral-based control strategy into the array layout design, this study aims to achieve an optimal WEC array layout that maximises energy absorption while considering the economic cost of the system. The proposed methodology provides a unique design approach that combines optimal layout design with optimal control performance. The analysis focuses on a three-device in-line WEC array, with different spacing and mooring arrangements. Energy capture and system cost evaluation are calculated, and the results obtained using the spectral-based controller are compared with those obtained using a benchmark passive controller. The findings underscore the importance of integrating advanced control strategies at the design stage to enhance energy absorption and cost reduction.