To sum it up you asked;
What is a boat worth and where do I start in order to buy it for resale??
Am I correct in interpreting what you wrote?
Needless to say 'This is my opinion:' and others will most certainly disagree, I am not infallible let's discuss it.
Boats are priced all over the place based primarily upon their owner's belief in what the boat is worth and somewhat on the general condition of the boat. They are just fiberglass, wood, steel and canvas.
It took me over one year to buy after I decided exactly which boat I wanted; I knew footage, brand, year range in mind and I knew exactly how much I was willing to pay and why. I looked at 20+ boats made only 3 separate offers before I bought my current boat. Toward the end of this process I could decide in 5 minutes if I wanted to inspect this boat or if I had just wasted my time driving over to look at it. I do not like to negotiate and I told them this when I made my offer, I was counter offered every time by the seller anyway. My first offer / counter offer taught me a lot about what I knew and what I thought I knew. When I actually bought I knew about what the market values were I knew about how long these boats stayed on the market, what sold them quickly and what did not sell them.
I have seen nice advertisements for Smelly rusty JUNK with original 20 year old equipment priced the highest on the market with the arrogantly delusional owner expressing the belief 'it's worth every penny'. Likewise, I have seen nice boats in good condition where the owner just wants to get rid of it quickly, priced at the bottom of the market. You have to look at a lot of boats to distinguish between these two extremes.
Nobody will say this way but, as the buyer YOU set the price. Do some serious research, if a survey costs 10% what are you willing to pay yourself to save an unnecessary survey? Read more than one book on boat buying, inspecting, repair, sailing and everything on the internet concerning your specific boat choice. There are numerous good boat buying checklists available online for free. This is after you make a decision on which boat to buy. Then with this knowledge make an offer based upon what you think this boat is worth and explain the reasons why to the seller. My last boat I bought for asking price, it was a fair asking price, I considered it way undervalued, he was making an emotional sell just to get rid of the boat which had been on the market 3 days. I didn't have to steal it from him to get a fair price. I felt then and still feel I could double my money in one week when I decide to sell it.
I donít subscribe to the survey prior to the offer method, if I have any doubts I walk away. Trust your instinct and do your homework. Then again I'm not financing a 750k 20 meter yacht. FYI, I have bought 3 sail boats in the past 9 years and have made money every time; first boat returned 300% second boat returned 100% and I am keeping my last purchase for a while, but I plan on returning 150-200% on it. Brokers/ dealers make a living this way, figure out what they do and just do as they do.
Surveys are not all bad insurance requires them, loans require them. My point is don't rely upon a surveyor to decide if the boat is in decent shape or right for you. If you are self educated an expensive survey should tell you nothing you did not already know. If you are self educated you will be surprised what a professional surveyor tells you they did not inspect that you did.