One quadrillion dollars: cost to remove CO2

These are my numbers. Are they correct?

There are about 3.0 x 10^12 tons of CO2 in the atmosphere.

40-50% of that is due to humans based on the carbon PPM rise since industrialization.

Stanford study and some hand math on algal biodiesel prices the cost to remove a ton of CO2 at $1,000.

so 1 to 1.5 trillion tons of CO2 x $1000 per ton:

1+ quadrillion dollars.

Comments welcome... the cost/ton of CO2 is the most fungible factor there... any insights?