Construction costs are currently skyrocketing

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.

That's something everyone has to decide for themselves, it's also a matter of preference.

Simply do it yourself. You don't need an architect or a [GU]. It's some work, but saves you easily 50 to 100k. Then lay floors, paint, build walls, etc. Do it yourself and save another 50k. Then it could work. You just need to have time or very little for 2 years.