If this issue is important to Tesla Motors - although I am not sure it is - there is one way they can proceed that will level the platform, and that is to emulate what we do at our lodge. I'll spell it out in generic terms, however.
An item has a putative cost of $X. Most customers ("A") are exposed to a state sales tax, so if that's 10% they pay $1.1X
Some customers ("B") have tax-free status (for example, state employees). Unadjusted, they would, of course, pay $X.
There are two ways to proceed so that all pay the same amount. One can:
*Increase the price of the good to "B" customers to 1.1X, or
*Decrease the price of the good to "A" customers to 0.90909X
Should Tesla proceed in analogous fashion? That is, so that those who can and those who cannot take advantage of the tax credit be treated so that all have a final payment of the same amount? Could it do so?
In order so to proceed, Tesla would need to know the tax filing status of its customers up to the point they achieve the production cap. Remember, the $7,500 tax credit itself is not a fixed amount - there is a sliding scale from 0 to 7500. Some of the Model 3-buying public obviously won't meet the minimum criteria necessary for the credit to begin to kick in; others obviously will be able to take advantage of the entire amount.....and many others won't know until they file their tax returns where in the middle they are. In order equitably to proceed, Tesla probably would have to be prepared to send some kind of rebate after April 15 of the following year....
Yecch. But I thought I'd throw out and explore the idea.