An example that sort of highlights my first point and sort of doesnt- a modern Shimano 5800 crankset search. Type in 'Shimano 5800 crankset' and choose 'used'. 3 items show up. 3. Really? Only 3 of these are for sale in the entire US on Ebay regardless of length or tooth count, and one of them isnt even a 5800 crnakset- its titled as Sora? So 2 used 5800 cranksets on all of ebay right now.
https://www.ebay.com/sch/i.html?_fro...Condition=3000
I am not looking for a 5800 crankset so this example doesnt really affect me, but assuming the search is correct(it looks to be), then while it isnt an example of me not knowing how to search anymore, it is an example of another anecdotal observation Ive had thru the last year- ebay has less stuff I want.
Im shocked there are only 2 used 5800 cranksets for sale right now in the US on ebay. Sure, there will be some bundled as a group too, but there are currently 2 used groups under 'Shimano 5800 group'. 'Shimano 5800 groupset' returns 0 results since the one it returns is a full bike. And 'Shimano 105 5800 group' returns the same 2 used groups as already mentioned.
Its crazy that there are only 2 listings for a 5800 group.
https://www.ebay.com/sch/i.html?_fro...Condition=3000
This is all modern product examples, but I used 5800 as an example due to its massive popularity and recency. If there arent many of a 40 year old item listed at any given time, the reasonable explanation is rarity.