Wow, in other states (WA) if you trade thru a "auto dealer" (which Tesla is) you only pay sales tax on the difference.
Found this from google: California, Hawaii, Kentucky, Maryland, Montana or Washington, D.C., you'll pay sales tax on the full price of the new vehicle, regardless of your trade-in allowance. Michigan changed its law in 2013 to exempt the first $2,000 of a trade-in from sales tax. The exemption will grow by $500 per year until it reaches $14,000.