GP just pulled a number out of the air. You could have just said it was disproportionate to the actual cost of concrete rather than reacting emotionally. I was surprised to learn concrete is only $130/ton, I thought it would be a lot more.

It doesn't really have anything to do with the price of concrete, though. It has to do with the price of carbon. If valuing carbon captured in concrete at $5000 per ton, the equivalent emissions tax on burning carbon is absurdly high.

It's a skill we all need to learn if we are to avoid completely missing the actual point and getting focused on the least important aspect of what somebody said.