I have seen those but found them less appealing. Storage systems seem to retain value better than compute nodes. Those almost 10 year old SAS2 storage enclosures in my original post still have some life left in them. As for the same age servers, they barely have any use.
Yet the server lot is going to sell for higher amount in the end. Go figure.
Several reasons why servers go for more than the price of disk shelves (or even head units):
a) Some are no longer supported by their manufacturers or require a maintenance contract for access (so no firmware updates unless you have a support contract at work that you can lean on, even for "final firmware release")
b) The shelves might have some nasty vendor lock-in (firmware checks, proprietary cables, who knows) that's not apparent until you try to connect them to another system.
c) The equipment might require 208v 3-phase (which is not available in most homes...not to say you cannot spend the money to put one in your garage for a plug-in EV, but unless you own a private house, that's not likely)
d) The price of the caddies to put on the disks might exceed the value of the shelves themselves
And to be specific about that particular auction, it's a mass disposal from a state of New York governmental complex, and you are REQUIRED to take all 68 shelves in a single lot AND figure out shipping yourself - the value on that bid is really just a peppercorn (symbolic amount to get it legally off the books), and I don't see the prices going up too much. The challenge is to figure out 67 other people who might want a disk shelf and arrange shipping/pickup on those units.