Quality is one thing, but usually what makes things increase in value is rarity and/or association. You can buy Strats made all over the world that will compete favorably with Fender's American-made units, often surpassing them. But, there are jillions of them, so they're not worth much, nor will they ever be no matter how old they get. Les Pauls are the same way. A '57 Gibson Les Paul might fetch 50K, but it's nowhere near as nice as an Agile 3000 series Paul copy you can get for $400. Thing is, there are only a few '57 Pauls. There are a jillion copies so they're not worth much, nor will they ever be. Most old guitars are junk, or close to it. But if it's rare, or somebody famous played it, that changes the picture.