[mlyle]

I think you need to discount possible farther future benefits, because so much change can intervene and make the analysis invalid.

That is, when people want to do something-- risks tend to be understated and possible future benefits tend to be overstated.

I don't back the precautionary principle, but I do think risk in cost-benefit analysis has to be viewed from a pretty cautious place, in general (not just science).

[Retric]

Ultimately, we don’t know the actual benefits and I just picked numbers from thin air to illiterate a point. But yea linear extrapolation of such estimates hundreds of years into the future is nonsense.