I ran into something like this last year when I was buying a hand gun. I live in California and I have to use a gun broker. I send money to the place where I'm buying the gun, they send the gun to the broker, he holds it for ten days and runs a background check on me, then I get the gun.
So, me and the broker are in California. I want to buy a gun from another state. The gun broker wants to collect CA sales tax (use tax) on the gun. Sounds fishy, right? Yeah.
The point became moot when I ended up buying from the Glock factory in Georgia. They collect sales tax in a lot of other states where they have vendors or something. That is, I paid sales tax to Glock and not to the gun broker. Same amount of money, but I didn't feel like I was being taken.
I do hope this free-for-all on cross-border sales tax lasts for decades to come.