Cost estimation for interior finishing, any experiences?

Hello! We are in a very early planning phase of our single-family house. Without specifically drawing in connections and electrical planning details, we made a floor plan with doors + windows in order to roughly calculate all areas. I have listed some cost estimates below, about which I am very uncertain and would like some advice.

The building is planned as a single-family house in Brandenburg (near Berlin) with a built-up area of 11.7m*10.37m including a basement with a white tank. The construction style is solid with a high-quality clinker facade (which has a striking color and is not in the "standard brick red" tone). Regarding energy measures, apart from the massive two-shell construction with good insulation (e.g., mineral fiber) and accordingly insulated roof, basement/floor slab and windows, only a geothermal heat pump will be used, which is excellently suited for the region (constant annual temperature > 10 °C already from 25m depth). From a cost/benefit perspective, I think very little of photovoltaic and solar systems. We also do not want a room ventilation system or similar because so far we all find them disturbingly loud (including the one in our current rental apartment), at least I do; my fiancée is not quite as sensitive.

I would now like feedback on how realistic some estimates are:
Deep drilling with a total of approx. 100 meters = 3,900 EUR
Heat pump e.g. geoTherm Plus from Vaillant with annual performance factor > 4 = 7,000 EUR
Bamboo parquet approx. 190 m² = 5,700 EUR
Tiles (approx. 190 m²) incl. tiled walls and high-quality tiles in the entrance area = 7,600 EUR
Insulation material approx. 250 m² 14 cm thick = 2,500 EUR
Facing brick/clinker approx. 250 m² = 7,500 EUR
Poroton hollow bricks + interior plaster approx. 250 m² = 12,500 EUR
Underfloor heating approx. 250 m² (some basement rooms are also to be heated) = 12,500 EUR
Basement with white tank approx. 80 m² usable area = 60,000 EUR
Windows and doors roughly estimated 25 pieces = 8,750 EUR
Additional construction costs (street connections) without official fees and construction water/electricity = 15,000 EUR

Altogether, my calculation (which also includes furniture, energy consulting, and such things) amounts to just over 200,000 EUR material costs. However, as I said, I am still quite uncertain about some of the above estimates.

For personnel costs (salaries), I have assumed costs of 180,000 EUR for a maximum of 15 skilled workers and a construction period of max. 6 months (with construction time guarantee). Is this a realistic assumption? Are significantly more or fewer skilled workers involved?

How are the [B]Vaillant devices classified?[/B]

I would already like to thank you for any support!

Your approach is, in my opinion, not effective...

Either go to an architect or a general contractor/general builder, explain your wishes to them, and have them prepare an offer...

Then you will see roughly where you stand price-wise... whether you end up choosing tiles for 40 or 30€ is secondary and depends on how well the costs have been kept in check until then.

And the thing with the controlled residential ventilation sounds more like poor planning/execution... the airflow should be so slow that on a normal setting there is no significant noise development...

Architects unfortunately do not do this very helpful work for free

But sometimes they do... at least the first drafts with rough cost estimates per m²...

Later you naturally pay for it... just like with the home construction companies...

Furthermore, craftsmen almost always calculate with a mixed calculation... meaning the craftsman partially finances himself through the material sold to the customer!

If you now buy the material yourself on the internet, the craftsman will, for example, no longer charge 100€ for installation but rather 250... or simply decline politely because he does not want to take responsibility for the "foreign" material...

The problem is just that all these home construction companies always offer things only from certain suppliers and you often don't get a good deal there.

Architect - specification of services - individual awarding of trades...

30 € per sqm bamboo parquet... are you going to carve that yourself? You just lay the parquet directly on the screed.
This item alone shows that you have planned at the very minimum. Apart from the fact that probably no one has all the prices memorized, hardly anyone will bother to research them for free.
Did you plan a total of 380,000 for your construction project, am I understanding that correctly?
It’s going to be tight, I would say, since you apparently also have higher-end requirements. (not meant negatively)

You can forget about internet prices, I would say. Go to a flooring store. You’ll see it starts at €40 and ends at €100/sqm. Even with bamboo, there are first, second, and third grades... We face the same problem, we want everything from one batch if possible, and online dealers already struggle with that. They say it’s cheap, so don’t make any demands. If you want to get construction materials yourself, go to the local building materials dealer and get offers there. You’ll only have problems over the internet. It starts with incorrect images and goes as far as wrong deliveries, or no deliveries because it’s currently out of stock. Sure, everything can go well, but the risk that something gets stuck is enormous. And what do the workers do if there’s no material? They’ll just send an invoice and go home, and if things go badly, they won’t finish in the specified time and move on to the next customer. That means extra costs. Aside from that, as a non-professional builder, you don’t think about so many things. I have read a lot, learned a lot, and am still surprised every day. I’m glad to have a professional general contractor who takes all that stuff off my hands. The bureaucratic hassle is enough for me.

Maybe I was a little misunderstood there. I have no intention of buying building materials on the internet or procuring them myself at all. My only concern is to read up on the subject BEFORE a consultation and a cost estimate by an architect/construction company, so that I have an idea of what should cost how much. Without accusing every provider of trying to rip me off, I still feel safer if I have at least a little idea about the prices. But as far as the parquet issue is concerned, we have already clarified that now. So if the construction company were to suggest bamboo parquet class 3 for 100 EUR / m², I would know something is wrong there.

Thanks anyway for the many answers so far, I have already learned 2 things:
- Architect is perhaps the better choice than construction company for many individual wishes
- My price expectation for bamboo parquet does not correspond to reality