Dwelling too much on price (and not condition)
The new-to-boats buyer tends to get hung up on the price, and I'm talking about used boats, not new boats.
The used boat is different from another used boat. It's somewhat like buying a car but with a difference. Most used cars are all alike (no DIY mods), save the options that were available at the time, like color, upholstery, convenience group packages, etc. These are factory-installed options, not DIY, and are all the same. After that, there are variables like where the vehicle is driven (rural dirt roads vs. urban paved roads, the "driven by a little old lady" and garaged vs. the parked outside suburb commuter vehicle, etc. Wear and tear like vehicle miles, upholstery damage, dings and dents are significant value determiners.
The Great Lakes and NE typically will have boats with less wear and tear because of the shorter boating season but they can also have freeze damage. I was just told about one boat that had a split keel (was not bolt-on) and engine damage due to freezing. Fresh water boats tend to get more blisters. On the other hand, UV damage is fierce on plastics. Then there is hurricane/storm damage.
Used boats, on the other hand, can have similar value determiners to cars, like engine hours, dings and dents, etc, but there is one other important area known as DIY modifications. Some boats tend to have numerous owner-installed modifications which are generally billed as "improvements" (look at any boat for sale ad to see a list). Unfortunately, I've seen many of these so-called improvements that are more damaging than beneficial and on a fiberglass and teak boat the damages are too expensive to un-do. Holes drilled through bulkheads to install speakers and TV/stereo systems, cockpit speaker installations, holes in the structural grid to run wires, owner varnished interior, etc. The list goes on.
Yesterday I was talked to a "new boat owner" couple that just acquired an older (1988) Fair Weather Mariner 39 that they bought. Part of the reason they bought it was because it did NOT have DIY "improvements". We discussed some of these so-called "improvements" we had seen on other boats and it was interesting that a long time sailor (he circumnavigated the world on his previous boat) and myself agreed on this DIY issue. They had the same problem with DIY butcher-jobs that did more harm than good and bought this boat because they didn't have to deal with correcting previous owner DIY projects.
Then there is the charter vs owner owned boat. Just like the rental car vs the privately owned car. And cars from the coast have more rust, then Washington and Oregon cars, even not on the coast, have more rust than California cars. Old collector cars from the '30s to the '50s bring more money in Washington if they are from California (but not from the coast).
Speaking of charter boats, liveaboard boats also tend to be more "used". The charter companies argue that "our boats are cleaned and maintained by professionals". Yes, but... sounds like the rental car sales places. Then there are cars that are advertised at being a "good commuter". Translated this usually means a "beater".
Area price variations (NE, S, Lakes, NW, SW), I suspect, to a large degree probably take into account the condition. Boats are reasonably mobile via truck or on their own bottom, so this will help to keep the resale market level.
In real estate they say "location, location, location". So for boats, what about "condition, condition, condition"?
Basically, each older used boat is different and should be considered on it's merits and not use a "blue book" cook book. If one wants to shop price then shop price ("beaters" are cheaper), but at least for me the condition, including DIY mods and maintenance (quality or lack thereof), is extremely important.