I think you're being disingenuous. It's not on the manufacturer to make sure the product has the right price tag on it, but on the seller or shop. European shop

I think you're being disingenuous. It's not on the manufacturer to make sure the product has the right price tag on it, but on the seller or shop. European shops put price labels on the shelves and their own tags on discounted or specialty goods. The online retail problem is also trivially solved. If I got to the US version of any online shop as a EU resident I'm usually first greeted by a "which version do you want to browse" popup asking me if I really want the US version and not a different country. This affects the default language, currency and locale as well as pricing. There's no reason they couldn't ask for your zip code if they already have to do these calculations at checkout anyway. The problem is that there's no reason US companies should do this because there's no competitive advantage in having transparent pricing. This would require legislation (probably at the federal level) but once there's regulations, you'd see these solutions pop up everywhere overnight. It's funny to hear Americans lament about how it's hard to do business in the EU because of the many differences between countries and then turn around and use state or county differences as an excuse why it's "just too hard" to do what companies are doing in the EU. At this point I wonder if Californians are seeing the same "sorry, we can't figure out how to show you this website without harvesting your data" error pages on US news sites given how strict their new privacy laws are.