Paying someone money to tell me if this boat could be fixed makes as much sense to me as finding a crashed damaged car, with an asking price that ignores the damage, and then paying someone to tell me if it can be repaired. Who does that?
Everyone who doesn't have the expertise to know for themselves how much the repairs will cost, or if they are possible.
For example, I once bought a collectors car that had serious engine problems. I made an offer based on my guess of what repairs would cost, but made the offer contingent on a mechanic checking it over. Once the mechanic told me exactly what the repairs would require (a whole new engine) I revised my offer based on that. In the end, I bought the car.
I have done the exact same when buying a house. Offer based on what I know, contingent on inspection. When the inspection revealed some unknowns the offer was modified.
Honestly, I don't know how else you think it COULD work.
The comment about "asking price that ignores the damage" is irrelevant. The seller can ask whatever they want. I can offer whatever I want. My offer will be based on what I know about what I'm buying (regardless of whether that is a house, a car, or a boat), and on what I consider it to be worth. It will NOT be based on what the seller is asking. The survey/inspection will inform me about things that I don't know.
So now I'm beginning to wonder, is it that you assume you have to offer 10% off of the sellers asking price (or some other number like that), rather than ignoring the asking price and offering what you think the item is worth? You keep bringing up what the seller is asking, and how they don't want to account for the needed repairs. Who cares? Again, the seller can ask whatever they want. I'm only going to offer what I think it is worth, taking into account what I already know, and contingent on having someone who is more knowledgeable than me tell me what I don't know. This is not backwards. This is exactly how it should, and does, work for almost all big-ticket items--cars, houses, boats, airplanes, etc.