Keep in mind Amtrak is an option on the PDX-PSC route. Perhaps not absolutely ideal--but an option.
Fares start at $35 each way.
Times:
PSC-PDX: 5:35am-10:10am
PDX-PSC: 4:45pm-8:47pm
It's a shave over four hours, so assuming your goal is to get to downtown PDX, it's actually not that much longer than a flight would be, once you account for arriving in time to clear security and transport from the airport to downtown in Portland (and vice versa). It's also quite a scenic ride through the Columbia Gorge.