Seems like UniquePlace on Amazon.de has it for €12.26 + €6 Worldwide shipping. The cheapest for Europeans on Amazon.de seems to be around €10 (which I've just purchased mine for), so giving €18 doesn't seem too unreasonable for shipping across the ocean.
I might be wrong on the shipping price, as the game might be labeled as a book, which would make Worldwide shipping around €15, as far as I can see. In that case, then you would be better of getting them from RheinTeam on Amazon.de for around €7 + €15 shipping. €22 is still not too bad, if the base game is anything to go by.