Construction costs are currently skyrocketing

I wouldn't be surprised if many architects or GCs now simply follow the maxim: whoever wants to afford many sqm also has the money, so I'll add a surcharge first

If I have to save, many would surely start with the sqm, calculating more tightly because "the competition" for 120sqm houses might be even higher than for 170-200sqm single-family houses

I have obtained five GC offers in the last three months. Of course, there were partly large price differences, but none of them even remotely came close to your amount. The only difference with us is the almost 180 m² spread over two floors, with a garage included. I do not have the feeling that I live in an economically weak region that would justify such price differences...

Why then with an architect? What in the end a general contractor (GU) can do just as well, or even cheaper.

I’m starting to ask myself the same question. In the coming weeks we will visit two general contractors (GUs) and cross-check this. Just looking at the price list of Viebrockhaus it seems like you might be able to get a bit more for that money (fully aware that there are still additional building overhead costs and extra requests).

The difference between architect and [GU] is not just in the price. It is also a completely different communication and responsibility structure

Although. How is that supposed to work anyway, or what does "shell construction" mean?
Heating and screed, windows and insulation, all that still has to be there.
That also means plastering must already be done, so electrical and sanitary installations too?

It's called extended shell construction.
That means
Painting work in the living room, kitchen, bathroom in the front house not carried out
Tiling work in the kitchen and bathroom front house not carried out
Parquet work / floor coverings in the living room in the front house not carried out
Interior doors and interior window sills
Glazing work, no shower enclosure in the front house bathroom
Sanitary objects no sanitary objects in the front house
Final electrical installation in the front house not carried out

It was an idea because we "wanted to save money"
If we also finished that, we would be at €723,000

We have 5 meters where we have to build to the boundary line, which many general contractors do not want to do.
But I can hardly imagine that justifies the high price?

The difference between architect and general contractor is not just the price. It is also a completely different communication and responsibility structure

In theory, yes. In practice, it depends on which site manager you get with the general contractor. And there are supposedly also architects whom you only see again at the final inspection after the groundbreaking...

I also don't see any advantages in the responsibility structure with the architect? With the general contractor, I pay a fixed price and the general contractor has to figure out how to manage with it. Do I pay the architect a fixed price? No, the trades settle with me in the end and it costs whatever it costs.

Of course, that also depends on the architect. But with the [GU], the goal is always to find the solution that is accepted with the least effort or cost. Not the best solution that fits the budget.