"At a conservative average fuel price of $3 per gallon, CARB's estimate
of annual fuel savings of $16 per car from reduced air-conditioner use
implies a fuel saving of 5 1/3 gallons per year, resulting in
cumulative avoided greenhouse gas emissions of under 0.6 tons of CO2
over 10 years. Applying the $70 per car estimated cost of the 2012
standard, it appears the cost of achieving these reductions comes in at
around $120 per ton.
Is that $70 per car cost a net cost (including savings), or the up front cost of the more expensive windshield? Assuming it's the latter, then you've got a slightly misleading estimate of the true "cost" of this abatement opportunity. If it saves $160 in fuel costs over 10 years, that's a total net savings (not a cost) of $90 - or a net savings of $150 per ton of avoided CO2.
Now of course, a dollar spent/saved today is worth more than a dollar spent/saved 10 years from now, so a more true accounting method would use a discount factor... but you get my point.
I'd also add that an increased cost of $70 on a new car costing $12k-$50k is a pretty miniscule added cost to be worried about. If the true cost of this was $120 per ton, that might be worth pushing back on. But if in reality, it's a net savings of any amount, then being concerned about an 'onerous regulation that precludes consumer choice' that raises the cost of a new car by a fraction of a percent strikes me as a waste of your otherwise well-directed analytic capability.