If you want to register a vehicle that you've purchased out of state in NJ, you have to pay sales tax on it, unless it was previously registered at your former address in the state where it was purchased. So basically, if you live in NJ and want a Tesla, you have to pay sales tax (and possibly registration fees) in the state you purchase it, and then pay sales tax AGAIN in order to register it in NJ.
That's true in most states. I got lucky in that I'd bought my car ~7 months before moving from New York City to Chicago...had I bought it 2 months later, I would have been stuck with sales tax in both states.
That said, as egregious as this is, it is nothing compared to the bullshit New York City and New York State inflict upon their residents. When I moved out of the state, I had to pay a punitive tax for having the audacity of leaving New York state. I kid you not. At around $3k, it's enough to hurt, but just under the amount that would make a lawsuit overturning this doubtlessly unconsitituional tax financially worthwile. That said, after this experience I will never willingly live in New York state again.