For the KOH-Ca looping process, Keith et al. explicitly state that they do not do a cost evaluation for a FOAK plant. Instead, they compare the cost of an "early plant" and NOAK plant. The early plant estimates from their study are $190-260 t-CO2 -1 when we escalate Keith et al.'s capture cost to net removed cost using their figure of 0.1 tonnes of CO2 emitted per tonne captured. However, our FOAK cost estimate is larger and ranges from $260-620 t-CO2 -1 in our harmonised framework for a case study in the USA paired to nuclear electricity. The main reason is that the contingencies that we apply are now reflective of the technology readiness level and detail of the engineering study. These contingencies also cascade into higher fixed operating and maintenance costs, which here are a function of capital cost. Meanwhile, the literature cost estimates of the KOH BPMED and MgO ambient weathering processes are said to be for a NOAK plant and are not comparable to the FOAK cost estimates here.