Thermoeconomic analysis was performed for high-temperature gas-cooled reactors (HTGRs) coupled with a steam methane reforming (SMR) plant in order to estimate the hydrogen production cost. Two possible HTGRs, a modified Brayton cycle HTGR (GT-HTGR) coupled with an SMR plant and a modified steam cycle HTGR (SC-HTGR) coupled with an SMR plant, were considered in this study. In these analyses, mass and energy conservation were applied strictly to each component of the system. Also, quantitative balances of the exergy and the exergetic cost for each component and for the whole system were carefully considered. The hydrogen production cost was estimated to be about $0.825/kg [$7.25/one million Btu (MM Btu)] for the GT-HTGR-SMR system and $0.728/kg ($6.41/MM Btu) for the ST-HTGR-SRM system with a uranium fuel cost of $8.40/MWh. The hydrogen production cost estimated in this study is considerably less than the economic target of $1.70/kg ($14.96/MM Btu), indicating that hydrogen production using HTGR with an SMR plant has great economic potential.