I almost purchased a 63 Jazzmaster guitar from a well regarded guitar shop (Kauffman's guitars) here in the Netherlands. It would have been all original apart from a refin and an added string tree.
On closer inspection after the initial purchase the following could be added in the list of mods; replaced fretboard (really good job though, hard too spot at first sight), tuners, pots, 1 pickup, wiring....
I handed them back the guitar, and they weren't too happy. Actually they were whizzed that I took off the pickguard to check as it's so vulnerable. They accused me that the pickguard got warped and shrunk in the short time it was with me, because I took it off for inspection which I should never have done. Luckily I kept screenshots from their initial listing which showed that nothing had changed while it was with me. But they tried to pull me off...
As for prices of old Fenders; you also often see it happen that sellers copy prices from other (reverb) sellers. Some add a little to that price as a margin, and after a while every 78 jazz is listed at €3500+....