So that you can roughly estimate it, our current construction costs:
We are currently building with a regional general contractor and our requirements were identical to yours (study, guest toilet downstairs, two children's rooms, separate master bathroom + dressing room) and are paying around 450k including outdoor facilities (lawn, terrace, driveway + carport) and tiling work. However, without a basement and "only" 140m2. The children's and study rooms are not the largest (each around 13 sqm), but that was already expensive enough. I grew up far worse and still made something of myself. Of course, you like to treat yourself to a lot, but you always have to stay realistic. For that, we put a lot of thought into the floor plan and adjusted and planned a lot of things sensibly. I didn't really get that impression from the neighbors in our new development (identical house from the outside). They just build away, but with a good floor plan you can really get a lot out of it. Every craftsman we talk to is surprised at how much better you can plan the house.
What I actually want to say is that the floor plan makes a huge difference.
In addition, we have:
[*]Nebenkosten 40k
[*]Erschließung, da Neubaugebiet 30k
[*]diverse Kosten von Ämtern (Grundbucheintrag, Hausnummer, Einmessung, Baugenehmigung) 4k
[*]Küche 16k
[*]Malerarbeiten 6k
[*]Bodenbelag 5k
All extra wishes, like extra sockets, double washbasin, shower niche, flush-mounted shower system, etc., are already included in the invoice.
So all in all about 550k for 140 sqm with your requirements without basement.
Although I have often seen that kitchens and painting work were sometimes much more expensive here.