Dams must resist various forces and remain economically viable. In this study, two dam types, a conventional concrete gravity dam and a roller-compacted concrete (RCC) dam, were designed, modeled, and analyzed under identical topographic conditions in Meshginshahr, where an earthfill dam already exists. A realistic cost estimation and comparative assessment were conducted for all three alternatives under equivalent site conditions. Cost differences were calculated using the 1404 national schedule of rates with quantity surveying and estimation software. Results showed that the RCC dam cost 49.58% less than the gravity dam, substantially reducing total project expenditure. The earthfill dam was 78% cheaper than the gravity dam because concrete works dominate gravity dam costs. Although the earthfill dam was 57% cheaper than the RCC dam, it is more vulnerable to seepage and offers lower stability than RCC structures. Therefore, from technical and economic perspectives, the RCC dam is the optimal option. Its advantages include lower cement consumption, minimal formwork, use of common road-construction equipment, faster execution, and reduced mobilization and project duration costs. Moreover, its favorable structural performance compared with earthfill dams makes RCC dams a more justifiable choice for future water infrastructure projects in similar terrains with constrained budgets and demanding safety requirements especially where rapid construction schedules durable materials limited maintenance needs and reliable long-term service life are essential priorities for planners and owners worldwide in many regions today globally.