The escalating water crisis in arid and semi-arid regions has transformed the reuse of treated wastewater from a technical option into a strategic necessity in water resources governance. Mashhad, as one of Iran’s major water-stressed cities, faces declining groundwater resources, increasing urban and industrial demand, and severe limitations in conventional water supplies. Under these conditions, the absence of a scientific wastewater pricing framework weakens economic signals, increases investment uncertainty, and prevents the environmental value of water reuse from being properly reflected in decision-making. This study aims to determine the optimal supply price of reclaimed wastewater per cubic meter in Mashhad using the Life Cycle Cost Analysis approach. The results of nine scenarios, based on three discount rates of 5%, 8%, and 10% and three operational lifetimes of 15, 20, and 25 years, indicate that the unit cost of reclaimed wastewater for the overall wastewater treatment system of Mashhad ranges from 299,483 to 466,023 IRR/m³. The estimated cost ranges from 312,849 to 485,565 IRR/m³ for new wastewater treatment plants designed for industrial applications, and from 257,077 to 403,996 IRR/m³ for old plants mainly used for agricultural reuse. The findings demonstrate that uniform pricing is economically inefficient and highlight the need for a gradual transition toward an economic, differentiated, and service-cost-based pricing system.