I bought a "Swan" concertina from McNeela several months ago, and they charged me the price listed on the website plus a 19 euro shipping fee (shipped to California), no tax or import duty fees.
A word of caution though: I recently contacted McNeela about their trade-in policy for upgrading to a nicer concertina, and they informed me that my several-months-old Swan concertina I just bought from them would only be worth about 35% of its original value as a trade-in toward a nicer instrument. I believe other makers (concertina connection, handmade models from irish concertina company, etc) offer a 100% trade-in toward higher end models.
Out of curiosity, which instrument are you interested in?