Is there a cost? I would say it is priceless - because we do not have any mechanism to funnel that money into undoing the CO2. And no, planting trees are not the opposite of taking oil from deep underground. Once that oil is out it remains in the above-surface carbon cycle. While it is underground it would never even be part of it. So any price would be made up - and just funneled to some interest group. The "compensation" does not actually compensate anything. This is the danger of only thinking in "money". I paid, problem magically solved!