Is cost calculation for a prefabricated house feasible? Are there additional costs?

Standard is _not equal to_ cheap!

Medium equipment from about 2500/sqm

Come on, let's keep things realistic. We are already building with very good equipment and around 200 sqm of living space. And with all additional costs "all-in," we are definitely staying below 500k. The current calculation is at 485k and we are almost finished. This includes the plot of land at 80k. We are then at 2,000 € per sqm, but including landscaping, garage, kitchen, stove... However, only the Energy Saving Ordinance, no KfW-x.

Then one should be able to manage well with 250,000 euros for 125 m² of living space, right? Also "only" Energy Saving Ordinance 2016... The plot is already available.. So the pure house finished and ready.. with kitchen but without furniture..

Then for 125 m² of living space, 250,000 euros should be enough, right? Also "only" the Energy Saving Ordinance 2016... The plot is already available... So the house itself ready and finished... with kitchen but without furniture...

I would say yes, it's possible. Even with a few more square meters. However, it very much depends on the general contractor/architect and, of course, the location.

Is in the village and we also want to carry out [Eigenleistung] ...

Well, don’t overestimate the savings from doing work yourself. You effectively only save on labor costs, and on paper, that suddenly looks pretty meager. We once had the electrical work calculated as an example. (have 6 electricians in our circle of friends) Savings just under 8k euros. And we lack a warranty (or is it called something else?). If the electrical work doesn’t work, I can’t blame the general contractor to fix it but have to do it myself. Somehow, that didn’t impress us. And you should never underestimate the time and stress factor of doing work yourself. Our neighbor has been finishing his prefabricated house for half a year. He’ll probably be done when we move in (We start construction in January). At first, his construction site was well staffed on weekends, now he’s working alone. His wife goes on vacation with the children alone now. He has to make progress on the construction site.