In this study, the effects of the cohesiveness of the soil in the area where the foundation will be built, and the earthquake risk of the region were examined on the construction costs of the diaphragm wall by the well method. Within the scope of the study, not only the soil in the region is cohesive or non-cohesive, but also the relative density of 0%, 50% or 100%, are discussed. In addition, different earthquake risk conditions such as low, medium or high risk of the region were taken into consideration. Thus, cost analyses were carried out in 27 regions with different conditions for the region where the diaphragm wall construction by the well method will be constructed. In the cost calculations, the Turkish Building Earthquake Code principles and the 2021-unit prices of the Ministry of Environment and Urbanization were used. For the diaphragm wall dimensions and quantity calculations, the IstCAD 2021 software program was used, and analyses were performed for each condition. It was aimed to determine under which conditions the well foundation construction would be more economical by comparing the obtained results with the studies in the literature. The study data advocates that earthquake risk makes significant changes in the costs.