They better as there are no reason they should be paid more than the Norwegian based pilots.
I don't believe that the swedish pilots should be paid more than the norwegian, but I dare anyone to make the claim that an FO pay difference of 15,000 kr per month after tax is fair when performing the exact same duties flying the same colors.
As for Sweden being cheap... what?? Oslo is filthy expensive, sure, but Stockholm isn't cheap by any stretch of the imagination.