As time goes by we have seen instances upon forum where you can hardly give these away as now very little demand, so was surprised to see how much two examples recently fetched upon Ebay:
https://www.ebay.com/itm/283586324777
https://www.ebay.com/itm/283564278802
Even allowing for fact that separate Jolla account has been setup so no need to purchase or arrange removal of existing Sailfish X license, €285 including shipping? Whilst I have no problem with seller trying to obtain this much having taken risk on obtaining "bootloader unlocked" device to re-sell, just wondered where demand is still coming from.

Incidentally XA2 Dual Sim similarly with SailfishOS license also up for sale @ €300 from same source:
https://www.ebay.com/itm/283564253795

Another seller trying it on and and doesn't explain that he/she willing to expedite removal of existing license, although stresses purchaser will need to obtain a new one:https://www.ebay.com/itm/Sony-Xperia...e/274021288026

And he has more devices
https://www.ebay.com/sch/os_outlet/m...p2047675.l2562
Don't know how they can sell them when i did not even managed to sell my F5121 for 100€ in a mint condition

So I should throw my as-new, unused XA2+ on the bay, you say?

Another seller has managed to sell two XA2 H4413 for €319 including shipping:
https://www.ebay.com/itm/Sony-Xperia...-/274017549622

Approach seems to be to promote as a Sailfish OS device (Buy-it now not auction) with its implied virtues, so whether increased demand for Google free alternative or buyers don't want "flashing hassle" whom can say? Obviously got it all wrong upon my XperiaX by taking TABackup to restore DRM thinking more appeal if restored to "factory state", when he sells one with Sailfish OS for about €200 with shipping:https://www.ebay.com/itm/Sony-Xperia...-/273984017029

Perhaps as forum users we assume that no one is going to pay extra for something you can do yourself, whilst user just wants it to work "out of the box".

Upon closer inspection, these all look like fake sales to me:
The first seller, os_outlet, has several identical devices, some "Sold", some available, same price, same everything, only the ebay item number is different.
Same for the second seller, minopodcast. Compare these two:
https://www.ebay.com/itm/Sony-Xperia...-/274017549622 ("Sold" for 289€)
https://www.ebay.com/itm/Sony-Xperia...cAAOSwYMldZrKI (for sale for exactly 10€ less)

I guess they're trying to convince potential buyers that these devices really go for that price, creating the impression of fake demand, trying to push the prices up.

I have had similar experiences just some days ago with Nokia N9.
The 16GB models can be had for 20-30€, but the 64GB are all on offer for ~100€, wherever you look.
It appears that nobody buys them for that price, but I still got abuse from one seller when I tried to even suggest some haggling.

I guess the tactic sometimes works.

In the end I bought mine from another seller for 80€ (although that one was listed for 100€, too, but they were more willing to haggle).
Still, compared to Android devices from that era, this is just crazy.

To answer your question "Still Demand?":
Yes, I think there's still a demand.
It's not in the numbers, but some people are obviously willing to pay a little more than what the market suggests.
These sellers probably file that away under "potential collector's item".
And online selling platforms make it easy to offer sth like that globally and hope for some mad sucker to come along and actually pay the price, because "I know I payed too much, but WTH, I really wanted that device".