Carbon dioxide removal (CDR) is a vital tool in the fight against climate change. The prevention of greenhouse gas (GHG) emissions should be a priority, but there is little doubt that CDR will be required to offset hard-to-abate emissions if we are to prevent the worst impacts of climate change and limit the planet's warming to 1.5℃ or even 2℃. Also, CDR is needed to achieve net-negative emissions once carbon neutrality of our economies has been reached. Bergman and Rinberg approximate that "hard-toavoid" emissions may be between 1.5-3.1 Gt-CO2,eq * year -1 by 2100, whilst the economic-optimised integrated assessment modelling pathways that result in 1.5°C of warming suggest that net-negative CO2 emissions are required from between 2040 and 2070. Direct air capture (DAC) and storage (DACS) is a technological solution to CDR. DAC entails the extraction of CO2 from air using (in most cases) a chemical sorbent and subsequent release of that CO2 from the sorbent. When that released CO2 is stored permanently, then this is DACS. As an approach to CDR, DACS facilitates comparatively easy carbon accounting and comparatively few external impacts, such as competition for land, than other approaches for CDR. However, it may also be costly and energy-intensive, and in some cases, waterintensive. There is a critical need for DACS cost estimates to underpin policymaking, integrated assessment modelling, and investment decisions. These estimates must be produced independently, i.e., by organisations other than DAC technology developers. As a result, several studies have attempted to estimate the current cost of DACS, or project the cost of DACS into the future. However, these studies all use methods inconsistent with the nature of the cost development of early-stage technologies, whose costs tend to rise during the research, development, and deployment (RD&D) phase up to the first deployed commercial scale plant, i.e., the first-of-a-kind (FOAK) plant, and then start falling as a function of deployment, as demonstrated in Figure . A recent method for the costing of advanced CO2 capture technologies was postulated by Rubin and co-workers. It is currently the only method consistent with the cost trajectory of early-stage, low technology readiness level (TRL), technologies.