EXTREMELY suspicious. Danger Will Robinson! In a bike town like Seattle, good bikes bring good prices. Only reason that would be cheap is if inherited and put up for sale without researching its value, or the internal gear hub is trashed and needs fixing.

EDIT: Wow, it is pretty banged up, paint badly damaged on frame and handlepost, unless that is just residue from removed stickers (possibly, as they seem to wrap around the frame, unless scraping to remove the stickers as they could be identifiers of the bike?), and damage to rear casters. Also worth less if has less than 6 speeds, like 3 or 2 or 1. So perhaps legit. But make sure you meet at their place or if just a public place, get their ID.