That boat is nearly 40 years old.
By 30 years, ALL of the deck hardware should have been re-bedded. By now the standing rig should have been replaced at least (!) once. Yeah, really.
*By comparison, in 2021 we replaced the second full set of standing rigging on our '88 boat.
IF the seller starts 'walking sideways' when asked about such normal albeit labor -intensive Preventative Maintenance, adjust your offer by about 10K. Or walk away.
If this clarifies your buying vision to the extent that you realize that a ton of used boats have a negative 'value', you are gaining wisdom.
While the Market will certainly determine the price of every used sailboat, you are not obligated to spend naive and ridiculous amounts of Your Money to play along.

Price is Not the same thing as Value.
Aside:
Insurance companies just want to reduce their chance of paying out for a repair or a loss. Like, reduce to near zero.
When they have documentation from a respected surveyor, and major maintenance documentation, they will agree to a value apropriate with your $$ investment. After all, they are really insuring an object, expressed as insuring your tied-up money. (Let's not call it an "investment"....

)
Another way to view it is that if you buy an older boat and spend 10K on it, that's the extent of your loss if it gets totaled due to the mast falling down, collision damage, fire damage, or flooding, or the old engine seizes up.
Now if you buy a fixer upper with 'good bones' and invest 50K in a restoration, AND your surveyor backs you up, you can reasonably ask for an insured "agreed value" of 60K. You will likely get it. As long as the chance of paying out is remote, the insurer just charges XX per thousand of value, and they make money and you sleep well at night.
Further Sidebar: the sailboat boom in the 70's and into the 80's produced a LOT of low quality fiberglass boats, and they are not very good/economical candidates for restoration. Especially so the ones at the bottom of the list. While we can all spend our boat BUC's however it makes us happy, spending money on restoring a solid Swan is always more defensible than throwing money at one of the flimsy low end boats. (And even the guy with that Swan will never get all of his dollars back, either!)
