Flat construction costs 2,000 EUR/m2

Kaldewei looks more modern at first glance than Villeroy & Boch

Optics are not the same as quality. You have to be able to tolerate it, but in terms of quality, Villeroy & Boch, Kaldewei, Ideal, Duravit are in a league of their own. You should not be dazzled by gimmicks. Concealed fittings are harder to maintain or even replace than exposed ones. And a rain shower is not better for showering than a normal shower.
A window does not become better because it is grey foiled; dark grey even causes it to warp in the summer sun. A concrete roof tile is cheaper than a clay roof tile, but just as durable. Among other things. In my opinion, it is not worth building far beyond the standard; the house will neither be more durable nor more habitable because of it, only more expensive. Karsten

When choosing bathroom ceramics, the switch program, or even interior doors, that may be true. However, there are also upgrades that make your house more durable and of higher quality, e.g.

Klinker statt Putz
Betondecke statt Holzdecke mit Rigipsplatte
Aluminium statt Kunststofffenster

None of this is standard, but it is hard to deny that with the mentioned things the house becomes more valuable.

Sanssouci Palace is a plastered house. It holds up quite well. PVC windows are just as durable as aluminum/wood. They are hybrid products anyway, with steel profiles inside and PVC on the outside. Wooden ceiling with drywall: A ceiling to the attic, which is hardly walked on, really doesn’t have to be made of concrete. An intermediate ceiling between floors is better, yes. Karsten

Purely in terms of the turnkey house price, we are below 2000€, including the expected additional costs for earthworks, surveying, etc., but slightly above. (Baunebenkosten, Einrichtung usw. kommen zusätzlich noch darauf)

As a first estimate, the 2000€ fits really surprisingly well.

Since I just read the post and came to similar results, here is my opinion on it.

I can now also only confirm the 2000€.
At the beginning, I assumed lower amounts, but meanwhile I have a fairly large Excel list comparing construction and service descriptions and prices.

If you want a solid equipment where everything has been thought of (starting with a construction site toilet, going through roller shutters, ending with enough sockets, ...) you end up at prefabricated houses (at least my comparison) at 2000€.

With a basement and a few small extras like electric roller shutters, you quickly reach 2500€.

At least this has been my experience so far. For all offers that were significantly below that, the wrong areas were economized on.