To obtain a maximum power output and minimized capital and operational costs, the layout of wave energy parks needs to be optimally designed. An economical model for large-scale wave energy systems is built and merged into an evolutionary optimization routine for arrays of point-absorbing energy converters. The model includes all the parameters that affect the total system revenue such as electrical cable lengths, distance from grid connection point, number of substations and hydrodynamic interaction among the devices, with the goal to find the optimal layout which minimizes the levelized cost of electricity. Converters inside the park are grouped in clusters via a k-means clustering algorithm, which allows to minimize the intra-array cable length under the input of real wave climates. The results show that the hydrodynamical interaction has a large impact on the optimal design of wave energy parks, and that the length of the intra-array cable does not play a significant role in the economical layout optimization routine for the studied wave energy park system.