Guy, I agree with you that buyers do generally not understand the difference between a good and a bad repair (me included). the reality is it could be either one, and unless you are a professional (your post sounds like you could be) then it's fair to say that buyers judgement could be wrong, and they stand to loose (maybe 80k) if they want that boat in seaworthy
If the seller had photos of the repair in each stage, the buyer could give this to a professional for an educated decision, and then you could make a claim that the boat is better engineered than from the factory.
With evidence of a stronger than factory engineering (repair) and honesty (with warranty) I would buy it!
Maybe professionals on this forum could provide a criteria of information that could be provided to buyers anyone wanted to sell a boat after a major $$$$ repair?