Is the basement cost estimate realistic?

What do you think is missing for a m2 created above ground? So why should the civil engineering, which is already more expensive than the building construction (among other things due to securing, sealing, lots of reinforced concrete instead of cheap stones, disposal of excavation), then be cheaper? Because of the slightly missing exterior plaster and the surface-mounted installation? Simple windows, by the way, cost about the same as masonry.

The costs for the excavation of the construction pit, etc. are explicitly not included in these costs. For me, these run under incidental construction costs, which were planned again with roughly the same amount. This is really only about putting a WU basement into the ground.

I also read that, but I just can't reconcile the numbers. That would mean construction costs of 162k€ for our basement. Could someone perhaps explain where these costs are supposed to come from? Are wet rooms, etc. being calculated here?

So our hobby room in the basement was significantly cheaper than the average living space otherwise. I also explain it with the lack of a bathroom and such.

However, the basement price was still within your price expectation and far from 35,000....

But even then, you only charge half the price compared to above ground. Sure, you forgo the two most expensive rooms in a house down there (kitchen and bathroom), but still: in the KfW-40 shell, partly underfloor heating, light wells, screed, floor covering, expensive reinforced concrete. 1250 per m2 is rather the absolute minimum.

There have already been discussions about similarly sized WU residential basements

https://www.hausbau-forum.de/threads/kalkulation-fuer-keller-wohnkeller-realistisch.26521/
https://www.hausbau-forum.de/threads/wohnkeller-ca-80-qm-wie-teuer.30751/

But that was 3 1/2 years and 2 1/2 years ago respectively, so you can add another 15 to 20% on top as of today.

So our basement cost just under 100k /pre-fabricated basement). 20 cm perimeter insulation on the outside, guest bathroom, hallway, and 2 rooms each planned as living space with 14 sqm. Thus a total of 40 sqm living area. Since it is a prefabricated house, I cannot break it down exactly because, for example, the screed was already included in the price as well as the electrical and water lines. But maybe it’s enough for a rough idea. Oh yes, the total area is about 60 sqm.

Our basement is also offered at around 100k. WU basement with 2 living rooms, a bathroom, hallway, technical room, and storage. The 100k is the pure basement cost; no fittings (underfloor heating, floor coverings, sanitary) are included yet. 51.89 sqm living area, 28.86 usable area. The offer includes the crane also for the house installation, portable toilet for the entire construction period, concrete work, statics, surveying, one light well, window openings, 20 cm insulation at the bottom and sides, filling and plastering. We are building about 30 km from Munich. The comparative offers were similarly priced.