I'm no accountant, but i have the impression that there are various international agreements in place that basically says that earnings are to be taxed where they are made.

This is why there has been a bunch of hoopla over Irish tax incentives for example, as it allowed the likes of Microsoft, Apple and Google to claim all sales inside EU was done by their Irish office. The rest simple earned just enough to cover expenses...

At least in the EU, you pay the tax where the company is registered, or in case of individuals - where you declare your tax residency is. If you own a German construction company that occasionally drives across the border to France and builds houses there, you pay taxes on your earnings in Germany, of course. If you work for a Swedish company in Malmo, but actually commute every day from Copenhagen(I know a few people who do that) you pay taxes on your salary in Denmark, because that's where you live and where your tax residency is.

It's a tax on import, not on earnings. The buyer would pay it, not the seller.