LOL for those who don't get his joke, its a traditional bathtub curve. Check some recent ebay sales... You want a new car or a PDP-8? An original Apple-I or an oceanfront house? True there's a gap of about a human generation in the middle where its scrap metal prices.

Also there's a strong supply/demand component. The supply of PDP-8 hardware is low enough that the prices are about the same per pound as silver, or at least copper. But PDP-11 and VAX equipment (currently...) has a large enough supply that its hard to exceed triple digits.