Let me explain: Over the last couple of month I've been looking to buy a certain used part (510/520 5/8ths saw blade arbor) on a well known internet auction site.

It seems like the majority of used Shopsmith parts actually do sell if they are in half-decent condition -- which I think is unusual in and of itself since on this auction site many non-Shopsmith items go unsold and get listed and re-listed many, many times. But the overwhelming majority of Shopsmith parts seem to sell.
In addition, many used Shopsmith parts sell for at or near (and as others have observed) sometimes above the retail price of a brand new part direct from the company itself. Seems kind of crazy, eh?
At the same time, whole machines seem to go unsold more often than any individual Shopsmith part and, when they do sell, whole machines sell for a tiny fraction of the retail price of a new machine almost regardless of condition (which probably explains why there are so many more parts for sale than whole machines on that site).
In sum, is a very strange economic market where machines depreciate very rapidly but their constituent parts do not appreciably depreciate (try saying that 10 times fast!) despite the fact that there is a large supply of both new and used parts to choose from. Meanwhile very few people are buying whole machines used (or new, judging by the company's financial problems over the last several years).
I'm not sure what explains all of this. Any economists out there care to try to explain it?