[CharlesWayneCT]

But not if there is a 9% MORE incentive to buy a used car than a new car.

Disparate taxation skews market forces. There is a reason Amazon fights like mad to not have to collect sales taxes — because that 5% or so state sales tax makes a big difference to their sales.

[Brookhaven]

But not if there is a 9% MORE incentive to buy a used car than a new car.

So, under they current system the price of a new car is $20,000.

Under the 9-9-9 plan, the retail price of the same car is $18,000 + 9% sales tax = $19,620.

$19,620 < $20,000

It would cost less to purchase the new car under the 9-9-9 plan.