I'm sure times and laws have changed, but in 1973 I was a student in California but a resident of Virginia. I needed to replace my car. Virginia didn't charge sales tax per se on cars but you paid the tax when you registered the first time. California charged a sales tax no matter where you lived. So I would have had to pay both California and Virginia sales tax on the single purchase. So I changed my residence to California! Alas, 9 months later I moved permanently to Oregon -- no sales tax and one of the lowest, if not the lowest, registration fees in the country. :-(