Your correct Flapbreaker, although of your short list, on the 25 hydraulic steering, trim tabs, and shore power are standard. Your right on with the rest. If you want a 25, a good electronics package including radar, a tandem axle trailer, wallas, or equivalent, and camper back. Then add a power windlass, anchor and rode and a VHF radio with antenna. In some cases a kicker and bracket. Now look at some of the custom items that will come along on many boats, Cabinetry, extra interior lighting, both white and red, upgraded wipers, intermitant wiper switches, windshield fans, AM/FM/Stereo, speakers, galley cabinets and storage, inverter.
Factory prices of the boats are just for the hull. When you add up all the rest you are, for all practical purposes, at $100K.
Oh, did you want a dingy. Most boats get sold with dock lines, and fenders also. I know, just a couple of hundred bucks. Couple here, couple there, I can come up with several thousand just in little things. On my trailer I have added a galvanized catwalk and bow ladder.
I see so many nice custom additions to many boats that I think generalization of used value is all over the place. I am sure there are used boats out there that you can get for a song in comparison to others of the same model. And if you are someone that wants a project boat that would be a good way to go. For example, one of the most pristine and well cared for 16's out there is Bambina here in the NW. 1989 and looks brand new. You can't compare Brocks Bambina to another 16 that is listed for $6000, because there is NO comparison to what you would get. (Bambina is not for sale, by the way).