It is best practice to evaluate the cost-efficiency of different road cut slope stabilization measures, prior to designing new cut slopes or stabilizing existing ones. This can be done by conducting a cost analysis. Most cost analysis methodologies require large datasets that are costly and time-consuming to establish (e.g. databases of historical data or in-situ test results). We present a new cost–benefit analysis (CBA) methodology based on direct cost estimates and a rigorous but parsimonious mechanistic and probabilistic geotechnical slope stability assessment that can be used to evaluate the cost-efficiency of different stabilization measures for a single-cut slope. Probabilistic stability analyses are coupled with a hillslope-hydrological model (the hillslope-storage Boussinesq model) based on the CUTSTAB-P method to determine the frequency of a cut slope failure over a prescribed period. By determining the frequency of the cut slope failure, the cost of failure (remediation) over a prescribed period is established. The cost of failure for a particular cut slope design is combined with the initial upfront investment and running maintenance costs to determine the cost efficiency of implementing the stabilization measures over the entire cut slope lifetime. This methodology is suitable to compare the cost efficiency of many different stabilization designs. Unlike other cost analyses for slope stability, our methodology accounts for uncertainty in slope geomaterial characteristics, as well as for hillslope hydrology.