Particularly anything that people already see as collectible and carefully preserve; leads to a large supply of good-condition items. Pocket watches are one in

Particularly anything that people already see as collectible and carefully preserve; leads to a large supply of good-condition items. Pocket watches are one interesting example. The majority of nice old pieces from the late 19th century are worth only $50-$80. It's something that seemed obviously valuable to people so nobody threw them away, even once they went out of fashion in actual use. So there are literally millions of pocket watches out there still, since everyone has their grandfather's old watch. And they regularly appear on eBay, keeping the market supplied. Even if a large proportion are cannibalized for parts or lost, it's still enough supply that collectors' demand doesn't push prices very high.