Are secondary construction costs realistic?

Hello community

We have now received a first offer for our prefabricated house (140 sqm living space without basement), I won’t say in advance from which company. Basically, my question is whether the construction costs are realistic; financially, it would be manageable for us and therefore ideal. But of course, we don’t want to fall into a trap.
In advance: There is no soil survey yet, but we assume that the ground should be uncomplicated. We are aware that this could still change.

Here is the breakdown:
House including foundation slab: 293,458
Plot including purchase ancillary costs: 62,200
Additional construction costs:
Building permit 1,000
Earthworks 15,000
House connections 8,000
Construction electricity, construction water 500
Surveying, guide frame 2,000
Soil survey 1,000
Architect house 5,500
Driveway, base for carport, base for terrace 5,000
Carport 8,000
Outdoor facilities in own work, material 2,000
Putty and painting material (own work) 3,000
Floor materials (own work) 4,000
Interior doors material (own work) 2,400
Kitchen 10,000
Buffer 20,000

Total: 443,058

What do you think?

... sent too early. The external dimensions would be 6.83 x 12.45, so around 85 sqm of area. The house is to have two full floors and a gable roof, kfw 40 with underfloor heating and air-to-water heat pump. Otherwise quite boring, no bay windows or similar.

Why make a secret out of the manufacturer? The manufacturer helps some who have already dealt with construction service descriptions here to better assess the offer. And guess what, "with Rosenthal" is not the motto in the forum.

Am I interpreting the self-performance points correctly that painting work, floor work, and doors are not included, but you want to do those yourselves?

Kitchen 10,000 euros ... depends on the requirements and could be too little.

Is it a semi-detached house?

Architect 5,500? For what? Seems very low to me.
Driveway, substructure carport, substructure terrace 5,000 ... how many sqm?
Outdoor facilities as self-performance, material 2,000 .... what is all supposed to include? Also fence?

Mhh, you’re of course right there. The offer is from Streif Haus. Not a duplex, no. Detached.

Yes, we are doing the painting, doors, and floors ourselves.

The architect is apparently a partner architect of Streif Haus, so I think the price could be realistic. (?)

Driveway and carport base are about 30 sqm. However, here we basically only need the materials and can do the rest ourselves. For the outdoor facilities, it’s basically just a hedge and a terrace with 12-15 sqm. But that will also be done ourselves.

10,000 for the kitchen also seems a bit tight to me, but it’s not a large kitchen – recreated with Ikea it’s doable. It’s not supposed to become a high-end kitchen yet.

I received an invoice today for the provisional construction power connection up to 80A from Bayernwerk amounting to €1050. These are not the consumption costs but the installation costs. This certainly won't break my neck, but I had not taken it into account in my calculation. Although it is actually just a drop in the bucket compared to your amount, maybe you want to consider it.

I received an invoice today from Bayernwerk for the provisional construction power connection up to 80A amounting to €1050. These are not the consumption costs but the installation costs. This certainly won’t break me, but I hadn’t taken it into account in my calculation. Although it’s really just a drop in the bucket compared to your total, maybe you still want to consider it.

Thanks, I’ll definitely include that!!