Go ask a builder.  Lots are scarce due to LCDC and Statewide land use planning.  Affordable single family homes in Corvallis get bought,  and a 4-plex goes up after the house is razed.  Why?  Because the land use goals say Corvallis,  home to giant PERS retirements,  H-P retirees with a pile of money,  has built too many 5-7000 square foot homes on quarter acre lots.  So for more than a decade,  it is urban infill and shared wall townhouses or apartment complexes.  The influx of rich Asian college students don't blink at $2000 rents.  They want concierge service, covered parking for a Mercedes.  OSU wants their tuition.  China wants OSU engineering expertise.  Our position in the world,  in a microcosm,  with LCDC and 1000 Fat Cats profiting from the squeeze.    

A  lot,  for a single family home,   is $75K  or more,  plus $20,000+ SDCs,  and $125/ft sq building costs for 2000 ft sq with a two car garage.   Viola'!  $395,000,  with some profit for subs and general.  Supply and demand.