If this is true, that is a monstrous 5% of an average new vehicle. And it's not just the cost of the vehicle, emissions equipment also can make the vehicle slightly less reliable, especially diesel engines, so it's likely to reduce the cost of vehicles by more than the initial 5%.
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I know for a fact the prices are lower non-emission vs emission. I own a tractor that is detuned 0.1 HP under the emission limit and with zero emissions controls. They sell the exact same tractor with the exact same engine with a fuel screw turned up over the limit to increase hp, plus emissions controls, and it's about $4,000 more. Manufacturers absolutely will charge more for emissions models than non-emissions models.