In fairness the Marantz is being purchased for a collector’s aesthetic - not just for a “value” PC which is the whole point of the old Xeon - the price rise is limited by this elasticity in demand.
And $850 I think is illustrative - that’s not unobtanium for middle class - it’s just happen to be a bit beyond what most people spend on a side hobby.
Similarly old Sun hardware either you’re screwed with a backward compat issue or again collecting since they are now vintage. x86 doesn’t have the former effect for the most part.