Retaining walls and cantilever soldier pile walls are both can be used in interchangeable manner so it is so important to evaluate the relationship between the cost and sizing. In this paper, an investigation of the effect of the design restraints and cost limits of both reinforced concrete retaining walls and cantilever soldier pile walls on optimum design is done. Pure frictional soils are evaluated as the surrounding soil medium of retaining structures and Rankine lateral earth pressure theory is used to derive the lateral thrust effected through the selected retaining systems. Fictionalized different cases are created for all retaining systems to compare optimal dimensions and minimum costs for the same project requirements. Jaya algorithm is used to perform optimization process. Parametrical analyses are conducted according to change of excavation depth, unit weight of soil, and cost of concrete, surcharge load and workmanship multiplier. The results of the parametric analysis has provided to suggest on the design and application differences of both retaining systems having regard to the effects of both cost and sizing simultaneously. As a consequence of the study, some limitations that have to be considered before design are given for the selection of proper retaining structure not to cause overinvestment.