I bought a Winchester Model 100 (.308 Semi-auto) at an uncle's estate sale. It was the first center-fire rifle I had ever fired; I was about 13, and he and I were hunting ground-squirrels with it.
Anyway, it had (key word - *had*) some sentimental value 30 years later, after Uncle Albert had died, so I paid dearly for it. I believe I gave about $325 or so , pretty much sight-unseen. The internals were filthy and corroded and pitted. It wouldn't extract when fired, and needed a new bolt, with extractor and ejector. And, the firing pin had never been replaced after the recall. About a $110 repair bill.
Of course it needed a 'scope, so I bought one, and mounts - another $200 (at least). By now, I have well over $600 in a rifle that's worth about $300 - as equipped.
I sold it several months later - prety much unused, except for test-firing - for ~$250, complete.
JB