My comments are as follows:

1. Obviously, this is not the current cost, but an estimate for a hypothetical future plant.

2. You can get wildly differing estimates through a series of small discrepancies in the assumptions. Comparing the provided estimate (Table 2 in above link) to the estimates for other CO2 capture projects the following things stand out immediately: a) 7.5% CRF calculation should be ignored as unrealistic, 12.5% CRF is okay; b) O&M costs are low, for complex plant with caustic chemicals and high temperatures a fair assumption may be 6% of CAPEX per year rather than approx 3% c) 20% contingencies at the conceptual stage are too low, 40% would be perhaps defensible. Also, I don't see a basis for including Row D in the table, the commercial assumption is not justified.

Considering the above, if all goes well, plant number 100 might be able to capture CO2 for $200-300/tonne, better than the current claimed $600/tonne for a plant actually in operation, but nowhere near as good as other options.