New process concepts, such as the swing adsorption reactor cluster (SARC) CO2 capture process, are often techno-economically investigated using idealized modeling assumptions. This study quantifies the impact of this practice by updating a previous economic assessment with results from an improved reactor model validated against recently completed SARC lab-scale demonstration experiments. The experimental comparison showed that the assumption of chemical equilibrium was valid, that the previously employed heat transfer coefficient was conservatively low, and that the required reduction of axial mixing could be easily achieved using simple perforated plates in the reactor. However, the assumption of insignificant effects of the hydrostatic pressure gradient needed to be revised. In the economic assessment, the negative effect of the hydrostatic pressure gradient was almost canceled out by deploying the experimentally observed heat transfer coefficients, resulting in a small net increase in CO2 avoidance costs of 2.8–4.8% relative to the unvalidated model. Further reductions in axial mixing via more perforated plates only brought minor benefits, but a shorter reactor enabled by the fast experimentally observed adsorption kinetics had a larger positive effect: halving the reactor height reduced CO2 avoidance costs by 13.3%. A new heat integration scheme feeding vacuum pressure steam raised from several low-grade heat sources to the SARC desorption step resulted in similar gains. When all improvements were combined, the optimal CO2 avoidance cost was 23.7% below the best result from prior works. The main uncertainty that needs to be overcome to realize the great economic potential of the SARC concept is long-term sorbent stability: mechanical stability must be improved substantially and long-term chemical stability under real flue gas conditions must be demonstrated.