Able to be viewed in person? That is probably the biggest deciding factor.
You said local and in WA, so good chance that it is actually rust free, but unless in person, truck has been re-painted a non factory color, so pictures are useless to determine rust (or past rust). Besides, IMO, rust through on replaceable body parts is less of a concern than the "rest of the truck" IMO, if one is looking for more than a pretty picture.
Things that detract from the "market value" if one is looking for a resto or resto mod project, vs looking for a daily driver old truck....if you're making a list.
Based simply off the picture..., not accounting for any mechanical or interior stuff.
- Non OEM grille
- non OEM bumper, although nice winch bumper
- And the big one. Non OEM paint.
-- Covers up previous damage
-- Not original looking and needs to be re-painted
-- Depending on how well it was painted = twice as much paint to strip off, or 3x or 4x...
-- How complete is the re-paint vs what is still original color (IE is it a complete repaint, or only the visible exterior surfaces)
My guess, not able to view in person/drive/verify if it's a bondo bucket or not, $6-7k, tops. It's an auction. If someone wanted to take the time to market it and show it and provide the perspective buyer reasonable opportunity to analyze the entire vehicle, and it's good, it would bring more money.
Also, not trying to bid the truck out from under you, but what auction is this and what auctions do you follow in WA? If you don't mind sharing. Can wait until the auction is over so no one get's turned on to this truck if you're really after it.