Price increase - Our construction company wants 21.4% more

read....wow....very cheap. With us, apartments already cost at least 3500€/m2 in the simplest equipment and without any extra wishes

I already know what is meant, no question. For orientation, this is definitely not wrong.

I see it much more differentiated nonetheless. With an average salary, I can look: industry / job --> salary - there are no major "exceptions" or things that can be different. I really know what an identical job in the identical industry can offer on average.

With a house, just a controlled residential ventilation system, a cistern, wood-aluminum windows, waterproof basement, fireplace, KfW 55 costs so much more that the price fluctuates easily by 20%. Thus, it becomes extremely difficult to orient oneself by it... this is just an example, which partly applies to us, causing the price to differ by easily 20% for the same m² size, in the same building area.

You can't really compare such things. Apartments have at least one more link in the value chain (shell builder, craftsmen, developer, sales, buyer) And above all, areas are externalized there, so they are not counted in the m2 of the apartment: staircases, elevator shafts and external corridors, storage rooms, heating cellar, laundry room, bicycle room, etc. But all of these are paid for proportionally! And elevators and increased fire protection are also things that do not occur in a single-family house in this way. Also, no own work is contributed here.

when you talk about 3500 per m2, things like those I mentioned are already included. When we talk about 2500 per m2 in a single-family house, spaces like sheds, garages or basements are still on top. And if it's built without a basement, you have to provide for storage space, utility room and heating inside your four walls, then you can no longer compare the m2 with those of an apartment where all of this is housed in the basement.

For basement (instead of slab), garage and shed you can roughly(!) calculate 30 to 50% extra of the bare house price, so you roughly come to your 3500. Fire protection requirements and an elevator come extra in the multi-family house.