ᐅ Single-family house with a separate apartment, double garage, and basement – construction costs of $1,000,000?

Dear Forum,

My husband and I are planning the construction project mentioned above. We have now received some initially shocking price estimates. Here are a few key details:

- Plot of land owned in North Rhine-Westphalia (rural area, not Rhineland)
- Single-family house with approximately 220 sqm (2,368 sq ft) of living space, including a 60 sqm (645 sq ft) granny flat, plus a waterproof concrete basement (WU concrete) of about 140 sqm (1,507 sq ft) – total: around 360 sqm (3,875 sq ft) of living / usable space
- Solid construction, brick veneer, 1.5 storeys, gable roof, pent roof dormer
- Plain architecture (no extravagant large window fronts, no floating stairs, no large spa or wellness areas; only luxury: an "external staircase" from the basement to the garage)
- Double garage (not a prefabricated garage)

Originally, we roughly estimated about €2,300 per sqm (square meter) average construction cost for the main house, plus €700 per sqm for the basement, plus €50,000 for the double garage. Based on these assumptions and a floor plan idea, we asked one national and one regional general contractor for rough turnkey construction quotes including interior finishing – the national contractor estimated between €800,000 and €850,000, the regional provider even nearly €1,000,000. In both cases, the basement was priced between €150,000 and €200,000, with the indication that a partial basement should allow for significant savings (how significant??).

Questions:
1. Is the estimated price for such a basement typical? We had actually planned for about €100,000 for the basement, i.e., around €700 per sqm.
2. Is a partial basement structurally so complex that overall it does not really pay off compared to a full basement? Or, given the size of the ground floor, is it financially reasonable to build a partial basement?
3. Is a WU concrete basement as a partial basement advisable regarding long-term waterproofing? Or put differently: Can one reasonably rely on a WU basement not needing to be excavated and waterproofed again in the future, which would surely be a nightmare for a partial basement?
4. Is a surcharge of around €100,000 for the insulated brick veneer facade normal for a house length of about 15 m (49 ft) and gable ends approximately 10 m (33 ft) wide? We have roughly around 150 sqm (1,615 sq ft) of facade area (excluding window areas).
5. What should we do?! 🙂
a) Reduce the size of the house? (This only makes sense if the price decreases roughly proportionally, which we did not expect – actually, we had not thought that a house with 220 sqm (2,368 sq ft) living space could cost almost twice as much as one with 150 sqm (1,615 sq ft).)
b) Skip the basement (difficult, since there is a lot of equipment and because of the layout with the granny flat on the ground floor, the floor plan is not very flexible)?
c) Instead of the house, cellar the garage? (Is it possible to excavate almost up to the property boundary? The garage has so far been planned as a boundary wall construction.)
d) Request quotes from additional construction companies?

We are sincerely grateful for any good advice. Until now, we had not expected to have so underestimated our - to our feeling generous - planning.