Trying to estimate the total costs of the externalities, like most economists currently suggest, is complete non-sense, in my opinion. Their methods are dubious to put it mildly [1], and they also replace the politically accepted goal with their own.

The politically accepted goal is to prevent dangerous levels of climate change. For this, we need to reach net-zero greenhouse gas emissions in 2050, according to the climatologists. Since there is no way to reduce emissions to zero until then (or possibly ever), we need negative emissions.

Right now, getting a metric tonne of CO2 out of the atmosphere costs about US$ 600 per tonne (with a sufficiently long or large contract). These costs may drop in the future if scaled-up but US$ 600 per tonne is the best estimate we have right now.

This is what emitters need to pay. Something around US$ 175 per tonne (+/- 75) would only buy about 30 percent of the negative emissions needed to reach net-zero. In other words, it's insufficient.

And of course this applies to everybody, not just rich people.

[1] https://doi.org/10.1080/14747731.2020.1807856