"You no longer own the car" - plenty of BMW, Mercedes and other premium brands customers don't want to own the car any more. They just want to lease it, get the updated model every few years and especially don't care to maintain it. In this context it makes sense to tax for a 20% increase in power. That will put significant additional stress and wear on the car so you need to cover the increased maintenance. Now I don't know if this is the exact context because the article doesn't really give details. Might be just a money grab that applies even to sold and post warranty cars.