10-4. I follow you now. Well, if Stark is charging a line item listed as "Sales Tax", they are not pocketing anything from that as that would be illegal. They have to turn that over to the entity (State or Local/City) for which they are collecting tax on behalf. So no way a tax can be an added fee in disguise that Stark is keeping.
But, agreed that there will likely be some confusion on their part on when they must collect sales tax. Not sure if there are dealerships in every state yet, but often the difference in a retailer collection sales tax or not depends on if they have a brick and mortar store in the State where the buyer resides. If yes, then they charge sales tax, and turn that over to the State, just like would occur of the buyer purchased as a brick and mortar. Starks come with a Certificate of Origin, unlike a Surron and others, so I would expect there is a good change Stark would collect your State (and maybe County/City) sales tax at the time of sale. And if that is the case, for two individuals living in the same zip code I would expect those that ordered after the price increase to pay the exact same percentage as a person that ordered before the increase. If that is the case, since the percent is the same but the sale price is $1,000 more, the second person would pay a dollar amount that is more.
Example:
6% sales tax on $13,000 = $780.
6% sales tax on $14,000 is $840.