Question about the magical 1,500€ per sqm

Cannot be answered.

1500 is a guideline, and in Munich this would certainly need to be raised somewhat.
Nothing can be said about the level of equipment either: There are sinks from Villeroy & Boch for 500€ and for 50€, the difference is usually only in the brand and the workmanship and ultimately the design.
For 1500€ you certainly won’t get a high-end equipment, but hopefully not just the cheapest junk either.

If you want to save money, you have to take it out of your contract and do it yourself/or buy it yourself at the hardware store. Because I believe the differences in material price won’t be that big, what might be cheaper for you is the labor.

Some builders have also reported building under 1500€, or are planning to. Unfortunately, hardly anyone gets back afterwards and says: it fits, or it didn’t fit.
We were significantly above that, and certainly don’t have luxury equipment. But also not hardware store junk. Wages are lower here too, but that didn’t matter with the nationwide house provider anyway.

Since I am also building only 60 km from Chemnitz, here is roughly my cost breakdown from memory. I think this is more helpful than a flat rate, especially since the construction company is also active in Chemnitz and maintains a show house there.

164K€ house, 2-story, 125m² (single-layer masonry without any frills) 10K€ surcharge for heat pump with ground collector for KfW 70 10K€ painting and flooring work 12-15K€ additional selection costs 15K€ outdoor facilities 22-25K€ incidental construction costs (the plot is level and the connections are already directly on the property) 47K€ land (of which 5K€ for the connections)

Construction started last week. Whether it will all work out in the end will become clear next year.

Thanks first of all for your answers! At the moment, we still lack the right feeling for a price per square meter (1,500 € or whatever). So far, we have only had contact with one general contractor. His first offer was almost exactly 1,450 € / sqm with a standard construction description (according to the provider = high quality). We suspect on the one hand that the 1,450 € is not yet the end of the negotiation range, but on the other hand, quite a few additional costs for sampling will come up for us (because, for example, we won't get anything that meets our ideas with 20 € / sqm for tiles or flooring).

Since I am also building only 60 km from Chemnitz, here is roughly my cost breakdown from memory.
I think this is more helpful than a flat rate, especially since the construction company is also active in Chemnitz and maintains a show house there.

164k€ house, 2 stories, 125m² (single-layer masonry without frills)
10k€ surcharge heat pump with slab collector for KfW 70
10k€ painting and flooring work
12-15k€ additional sampling costs
15k€ outdoor facilities
22-25k€ incidental building costs (the plot is flat and the connections are already directly on the plot)
47k€ plot (of which 5k€ for the connections)

That would mean, you have basically paid 164k€ for the house + 10k€ for painting and flooring = move-in ready house according to standard construction description a total of 174k€ = 1,392 € / sqm, right? Are you available for further questions via PM?

You overlook the sample selection and approximately 30,000 ancillary construction costs.

I have now recalculated... because: I pretty much didn’t care about the price per sqm, because: I have the demand x and can pay costs y... I paid more attention to the reputation and quality of the BU (even if I didn’t like the conditions in hindsight)
So we come to about 1400 €/sqm + 10,000 for upgrades (sanitary, tiles, electrics) + ancillary construction costs + EL painter and flooring.
Construction area: northern Lower Saxony, construction trades in the Hannover/Celle area... should be very cheap.
With Heinz von Heiden I would certainly have saved a bit more, but certainly not my nerves and my expert.

I would advise not to look for the cheapest provider per sqm, but to take the one that gives the best gut feeling... let it be 50 € more... in standard, most have similar objects or number of sockets anyway. Extras like a second outdoor water tap, outdoor lighting or additional circuits, thermostats in the shower or possibly 30/60 tiles are included by very few in the construction service description, and that is then the additional customization.

Turnkey house (including flooring + painting) exactly 1,500 €/sqm
Basement ([weiße Wanne]): approx. 690 €/sqm usable area
Additional construction costs will be added on top.