Remember also that SAS has recently started selling one way tickets for domestic travel within the Scandinavian countries, as well as for travel in the Scandinavian "triangle" - CPH, ARN, OSL.
Well worth a look. Prices for intra-Scandinavian travel is approx 550SEK (approx. 70USD). And intra Sweden is 390SEK (approx. 50USD). All including taxes.