Defensive offer, or have house prices become so expensive?

No, to be honest, I would skip the second reviewer.

If you mean me.... No second reviewer, that doesn’t make any sense; what I meant is that it would be important to me that the person who will ultimately implement it technically is involved or included as much as possible (if possible).

We also plan to build, but we are very surprised by the price that was quoted to us yesterday. There was a preliminary discussion about our wishes: 160 sqm; KFW40+; basement; 3 children's rooms, etc. With land for about €100,000 and all additional costs (garage, garden, terrace, kitchen, furniture) we have arrived at a turnkey house price of €890,000. My wife and I are still very young, 26, but do not know how to pay for this!

Yes, that's how it is nowadays. Either build smaller and not quite as high-quality (KfW40+ is only one level below the passive house) or use existing buildings. A basement costs on average 100,000 EUR. With more ancillary construction costs, probably even 120,000 EUR.

Your construction site would still be interesting.

We also plan to build, but we are very surprised by the price quoted to us yesterday. There was a preliminary discussion with our wishes 160sqm; KFW40+; basement; 3 children's rooms, etc. Including land for approx. €100,000 and all additional costs (garage, garden, terrace, kitchen, furniture) we arrived at a turnkey house price of €890,000. My wife and I are still very young, 26, but we don't know how to pay for this!

Where is the problem? Basement, KFW 40, 3 children's rooms, 20sqm living space leave out and done

Instead of a garage, a carport or initially a free parking space will do. The roof can come later. Oh, by the way, you are still allowed to build according to the Energy Saving Ordinance. Probably not anymore during the course of this year, but in some cases the start of construction is already with the demolition, otherwise with the beginning of earthworks, which you could theoretically do months before the foundation slab...

There was a preliminary discussion with our wishes 160sqm; KFW40+; basement; 3 children's rooms, etc. With the plot for approx. €100,000 and all additional costs (garage, garden, terrace, kitchen, furniture) we came to a turnkey house price of €890,000.

Quite normal in the first planning phase when you want to have everything at first. There is a reason why most people actually want a basement but then don't build one. This also applies to a few other mentioned points.