The main thing is that open hole flutes are really only popular in US. In Japan, you will find very high quality plateau flutes. That said, if you can find a Muramatsu or Miyazawa plateau flute in the US, it probably will sell for pretty cheap.

I have no idea if this would be an issue for a flute, but there could be customs/import duty taxes involved. But again, I have no clue on that, just putting it out there.

Yes that is correct. There will be.