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".