That doesn't make sense because the second hand car is not cheaper by the amount of the subsidy. Say subsidy is $20k, second-hand car might eventually be $6k cheaper (and the discount time value of money means that the $6k is actually less than $4k). Giving the wealthy person $20k, and the poor person less than $4k is strange.
New Zealand used car market is likely very different from the market where you are. The cheapest Model 3 I could find was a USD18000 for a 2020.
Subsidies make sense if the environmental gains outweigh the costs of the subsidies.
Subsidies: there was a purchase subsidy, charging stations were subsidised, and I think electric cars are not paying their fair share of road maintenance (much of our road costs are paid for by an excise tax on usage via petrol-tax or heavy-vehicle-milage).
That math doesn’t add up. If I buy a $100,000 car for $80,000, and I sell it to someone for $60,000, the recipient still gets a $40,000 discount.
And if you pretend that there is no subsidy, and the original owner paid $80,000 just because it cost that much unsubsidized, the second buyer still gets the same discount off the original purchase price.
So the fact that the car was originally subsidized isn’t relevant.
The context is about when cars reach the poor - your example of someone spending $60k is irrelevant.
A poorer person in NZ spends at most a few thousand on their car. The original retail price is nearly irrelevant by the time it gets to someone poorish (however maintenance/parts costs do matter for old cars).
The financial benefit of a discount mostly goes to the people that own the car while it depreciates as it trickles down.
Context: In New Zealand, the vast majority of people drive second hand cars (mostly imported second hand from Japan). A 20 year old car is regarded as newish in New Zealand. I am well off, so I have two second hand cars, my daily driver is 2006 I think, and I have a 1996 4WD for other stuff. New cars are only bought by the well off.