Right now, some will give a crew rate (Quality Inn is around $50/55)
Comfort Inn
Clarion
Red Lion
BUT...we're approaching cruise season, and SEA (all of Seattle) runs about 85/90% occupancy...so there are literally no cheap rooms starting in May. There are some decent crashpads around (I run one, so if you're looking longer term, I'll let you know when I get available beds)