Single-family house, hillside location, basement half residential/useful area - expensive shell construction?

Hi,

we already have a plot, it is on a slope, which can be compensated by exactly one floor height.
Therefore, there should be a basement, which offers two living rooms (above ground with windows and a door to the garden) on one half and two cellar rooms on the other half (two light wells).

The exterior floor plan dimensions are 8.60m x 9.60m.
Fully brick-clad in the above-ground part, 45° gable roof, dormer.
KfW55 with ventilation system.
Overall about 170m² of usable and living space.

The street runs above / uphill.

We have been in talks with two developers and have conducted planning (so far free of charge for us).
Both offered about €275,000 for painter readiness.
For both, the shell construction should cost about €191,000.
And I think that is exaggerated. That is almost 70% of the total sum. On the internet, I often read about 45%, which the shell construction would account for as a share of the total volume.

In advance, it was often said that a basement is very expensive, €50,000, I have even heard €60,000.
Others speak of €25,000.
Ok, the living rooms in the basement now have underfloor heating and windows and a front door, which also costs €2,500 there. And one more brick height is used in the basement to achieve a clear height >2.40m.
But €190,000.....

Or am I barking up the wrong tree here?

A residential basement finished with insulation in that size costs at least 70-80k.

It’s not just the additional floor height but also the pipes, concealed wiring, etc.

PS. The basements for 25k are bait offers without stairs, electrical work, etc.

I recalculated. The painter-ready offer came to 275,000. All finishing trades were quoted together at 75,000€. That means the shell construction even costs 200,000€

Well, I am talking about the shell construction.
Let's leave the basement without finishing (electrical etc.) at 40-50.
The rest of the shell construction for a 1.5-story brick-clad house still costs 150,000€. (The brick portion is about 15,000€ including the above-ground part of the basement).

Assuming I leave out the basement, then the shell construction for 8.5m x 9.6m would be twice as expensive as the interior finishing.
Am I wrong? Something doesn't add up.

Well, the roof structure also costs a lot.
Windows and doors too.

You probably have a flaw in your thinking.

Or am I barking up the wrong tree here?

Recommendation: don't argue, just sign one of the two contracts!

I consider TEUR 275 – under the above-mentioned conditions – pure wishful thinking. However, if your preferred candidate thinks he can build at this price – and the contract reflects your wishes in writing, then it shouldn't matter to you.

Rhenish regards

I had about 10 different offers from general contractors, prefabricated house manufacturers, and also requested everything myself from smaller companies. (submitted the same plan from the architect to all of them). In the end, all offers are quite similar and for a comparable size of 170m² and without a slope (which also has to be supported due to the gradient of one floor), our offers always started with a 4. Therefore, I see your offer as very, very good unless there is some catch somewhere.