It appears to be estimate of an economic modeling number, not indicative of market prices.  We will see how accurate such a number might be if and when USDA is instructed to monetarily incentivize carbon capture.

My buddy tells me right how you can still replace coal/oil electricity with solar at a carbon cost of $1/ton for companies who need to make good on promises to environmental advocates, but I assume that market will saturate at some point.  But until it does, $100/ton CO2 capture seems to have a lot of market forces that would push the price back down.