A.F.
Hi J.! I don't know if this helps but I have always had better prices through a travel agent. I was a frequent visitor to Seattle and the absolute best prices I discovered were when I would fly Sun Country into SeaTac and take the midnight Northwest flight home. I don't know if the schedules have changed in the last couple of years but for the 3 years that I traveled that route it worked out so well!
Happy traveling!