You must look in the wrong places.
When looking at my "finished auctions" on the auction sites I frequent, pretty much every single DS is within the price bracket I mentioned. I follow Certina auctions on a number of sales sites daily and if something interesting comes up for sale I will monitor how it progresses.
https://www.ebay.com/itm/154926196308?hash=item2412522654:g:qgYAAOSwbkRiRfsi&nma=true&si=sFCqtxogH8Lktm63Z2bnsVFMVVM%3D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557
Early, correct crown, really clean dial, excellent case. Looking at how clear the texture on the turtle shield on the caseback is, I would say that this will look fantastic after a clean up.
€142. Sold on eBay in an open auction for everyone to see.
If a DS has a higher asking price, it better be a pretty great specimen.
The non-turtleback DS for sale you link to will probably remain unsold at that price. Sellers can ask whatever they like and this one will likely sit for a long time before moving - at a lower price. BTW, you are aware that the earlier Patent Pending references, all things being equal, are more expensive than the ones with the turtle?
@Fadershan, you got this one for around €170 recently, how did it turn out? It looks like both dial, hands and case are excellent, but the crystal, naturally, needed changing?
Top DS' are in demand and command a fair bit of a premium. But look at this one, which has a period box, some paraphanelia, a great looking (later) bracelet and an excellent case - and see how much it ended at, probably due to a degraded dial:
https://www.ebay.com/itm/Vintage-Ne...83.l44720.c10&nordt=true&rt=nc&orig_cvip=true
$358... The bracelet alone will be $200.
In short - I cannot recognise any trend supporting your claim about the general price level and that is something we all should be happy about. DS' remains an attractive and fairly cheap entry to the solid vintage everyday/sports watch, far cheaper than similar Omegas.