Realistic costs for a single-family house?

Just reviewed the house wish again. We are looking at 2 full floors with LWWP, underfloor heating, controlled residential ventilation, basement, electric shutters, and a living area above ground of around 144 m² at around 315k without floor coverings and garage.

Insider tile trade made me laugh. I would reconsider wall-to-ceiling tiles in bathrooms – if so, design them creatively; with only white it looks like a laundry room. Including garage, floor coverings and co., it is rather inexpensive.

100,000 for auxiliary construction costs and the plot? Do you mean additional costs for the plot?

With a basement, you will barely stay under 400k, that is correct. With a garage and in the size you have set, you will definitely end up over 400.

Insider tile trade I had to laugh.
I would reconsider floor-to-ceiling tiles in bathrooms - if then design creatively; with just white it looks like a laundry room.

Including garage, flooring, and stuff, it is rather cheap.

The garage is in the basement, so not a separate building!
We will do quite a bit with decorative tiles in the bathrooms.
And I don't really find it cheap, but I guess that's normal by now.

100,000 for incidental construction costs and land? Do you mean incidental costs of the land?

No, about 50 k€ for the land and 50 k€ for incidental construction costs, otherwise I would have written acquisition incidental costs and not construction incidental costs