Worth is personal, to a point.
In locating my hull, I had specific things in mind, and the fact that the interior was in poor shape had little bearing on my final choice, as it is my intent (the scope of the project) to customize it to suit myself. So very few boats out there would have met my needs off the shelf anyway.
Having just spent part of this morning looking at a "project" that was sadly not salvageable, and being one of those sorts of dreamers that feels sadness at the thought of a fine old hull disintegrating through neglect, I suppose any reader can quickly peg me as "one of those"...
Since most (I'm sure the yacht brokers would quibble and I wouldn't argue that their viewpoint is invalid, at least from their standpoint) would agree that resale value has little to do with worth, you have to decide somewhere along the line what you're going to commit to a project.
And is it something with a big budget up front, or will it be a little along (which is the typical American backyard mechanic's way of doing things)?