Within the past year, I bought what sounds like a similar vintage, perhaps similarly equipped boat, in a similar area of the country. Without even seeing photos of the boat and/or trailer there are a lot of unanswered questions, but it would have to be a real wreck to only be worth $12k. Seriously. Don't go by NADA.
I would guess something around $30k, variability up or down depending on the fine points, such as the following:
Single or tandem trailer and does it have things like disc brakes
Hours on engine; whether or not there is a kicker engine
Condition of gelcoat and upholstery
Existence of canvas and condition
Type and vintage of navigation electronics
Trim tabs (does it have)
Hydraulic steering or cable
Electric wipers or manual
Windlass and ground tackle
Autopilot?
Floorboards?
Sliding co-pilot seat?
I will say that C-Dorys do not seem to fetch as much in the mid-Atlantic/SE as they do in, say, the PNW (which makes sense since they are PNW-built boats), but $12k still sounds completely unrealistic unless it's in the worst possible condition (and it would have to be bad). I would expect that sort of price on an older boat in "rode hard and put away wet" condition, faded, dinged, maybe with an original 2-stroke 70hp engine, or even no engine, and a single-axle trailer.
If you go to the Classifieds sub-forum here, you will see a thing called "Marketplace reference." This doesn't show the selling price (just the asking), but you can get a pretty good idea based on asking price plus how long the boat took to sell.
Sunbeam :hot