The ticketing and fare calculation is done based on the country of residence in your profile stored on the site. The low price on the wesite ends the moment you log in or give them your address where they should send your eticket receipt. So technically you have to give an address in the country whose website is showing the good price.

All intra scandic tickets booked on the german country site are chepaer because sas doesn't charge the various booking fees here.

Regards Oliver