If you go some American sites they have a note that covers this problem.
I'm from Canada , I have the same problem with airlines. Flights to/from Asia are cheaper
if bought thru their Asian sites. I still get charged to Canadian price for the ticket.
This I found also happens to us if try to book cheap flights on some American carriers.
SS Ithaca , Volendam , Mariner of the Seas (x2) , Veendam , Coral Princess , Island Princess (x3) , Emerald Princess,Sapphire Sapphire (x3),Diamond Princess