Architect's cost estimate realistic?

Is there a detailed cost breakdown from the architect, where the individual amounts listed above are itemized, or did he just roll 5 numbers and present them to you?
Without further information, the figures are meaningless.
There must be a reason why he is so far above the average.

Otherwise, I agree with nordanney... with the appropriate equipment, you can quickly reach such values.

Sure, with the appropriate equipment, but that was neither requested nor communicated.
The specification was KFW 55, standard equipment, no frills like smart home, aluminum windows, special floor coverings, etc.

No, the costs are not itemized. It is only a rough cost estimate.
BGF is specified as 260 m2 and BRI as 910 m3.
The 700 costs are broken down, but I don’t think that really helps, does it?

7.1	LPH1-4	12000
7.2	LPH5-9	50000
7.3	Surveying	1600
7.4	Structural planning	7000
7.5	Verification statics	3000
7.6	Soil investigation report	2500
7.7	Specialist planning	-
7.8	Energy consultant	2000
7.9	Safety and health coordinator	-
7.10	Building permit	3000

No, the costs are not broken down. It is only a rough cost estimate. GFA is given as 260 m2 and GVI as 910 m3

How do you get 910 cbm from 125 sqm living space? That is a cuboid of 10x10x9m. Or rather with 260 sqm GFA = 125 sqm living space. ==> There is a huge error in your numbers, probably in the living space. For comparison: My two-family house actually has 910 cbm (no joke!) without the extension, but 160 sqm living space plus about 25-30 sqm hallway/staircase areas. P.S. In single-family houses, on average about 70-75% of the GFA is the living space.

Yes, that is probably true. But it is more likely a mistake by the architect if I say I want 125 sqm of living space and receive an offer in the range between 180 - 200 sqm, right? The building must have a very high and steep roof because of the outbuilding. However, the roof is not supposed to be developed. I am assuming 3 full floors plus the roof. Then I would have about 55-60 sqm of floor space per floor. That would be approximately 10x6m floor area. Then I would end up with a gross floor area of 165-180 sqm. Then I would take 70-75% of that to get to 125 sqm of living space, right?

Yes, that is probably true. But it’s more likely a mistake by the architect if I say I want 125 sqm of living space and get an offer in the range of 180 - 200 sqm, right?
Because of the outbuilding, the building must have a very high and steep roof. But the roof is not supposed to be converted.
I assume 3 full floors plus the roof.
Then I should have about 55-60 sqm of floor area per floor. That would be roughly 10x6m floor area.
Then I would end up with a gross floor area of 165-180 sqm.
And then 70-75% of that to get to 125 sqm of living space, right?

Yep. Sounds like it.

Is there not yet any concrete house planning or area/volume calculation from which these numbers can be read?

No, unfortunately, they do not exist.

I have calculated with the BKI planning tool using the construction price index 01/2024 (163.3). According to the table, the architect calculates 1500€ for the 300s and 388€ for the 400s.

In the BKI planning tool, which the architect also uses, a value between 1065€ and 1343€ is given for the regional factor for the 300s costs.
For the 400s, a value between 205€ and 345€.

I have now taken the highest values each time.
So I come to the following values with a GFA of 260:

1343€ * 260 = 349180
345€ * 260 = 89700

Then the 300/400 are at 438,880 euros. That fits better with what I have calculated...

But as you already said, one is an estimate, the other is real life.

Of course, the BGF does not fit our requirements/expectations, as it is still, unchanged, too large.