Depends on state but for me.
NJ no sales tax on EVs
If I want to upgrade the battery pack from 60 to 75. I need to pay sales tax on that upgrade.
Yes, the no sales tax on EVs in NJ is one of the many reasons why I’m getting the Model 3. For NJ residents it definitely makes sense to get EAP when you buy the car. If not then the cost of the EAP upgrade is not only $1000 extra, but you’ve got around $400 in sales tax thrown onto that as well ($6000 EAP upgrade after purchase X 6.625% NJ sales tax, the new tax rate in 2018). So getting EAP after buying the Model 3 in NJ would cost you $1400 more. If you get EAP when you buy the car then that $5000 option is part of the price of the car and not taxed by NJ.