I bet this issue is happening on all carriers.... Nobody ain't gonna pay $251++ to fly LAX-PDX... Rip-off fares, I think PDX is going to be the next CVG where the average fares are ridiculously high.
Also, the business/government sector is not as big in PDX compared to other cities, so this route depends on significant amount of VFR traffic. So, with $250 fares, people will only go to PDX only if necessary, not for pure enjoyment.
Until the fares for this route goes down around the same level as LAX-DEN, they won't be seeing much traffic. Welcome to the era of the customer-centric market. If we do not value the price for the service we will obtain, you betcha we ain't flying!