Stop or pause house construction? Costs too high

The contract with the architect comes about just as easily as the contract at the baker when you buy a roll. No special formalities or form requirements. Oral agreement and corresponding actions are completely sufficient.

so why written contracts for work then. Everything is oral. Of course, there is no doubt about the validity, only the fee is usually based on the construction sum.

Of course, there is no doubt about the validity, but the fee is usually based on the construction sum.

However, there is no construction sum here yet. The architect's estimate alone does not constitute a basis for calculating his fee.

I don’t think it takes much to get a misunderstanding about the budget: the initial post talks about "just everything quite normal, actually standard things" and then lists almost 200 sqm, KfW insulation stuff, and an attached double garage. If someone sits with an architect who happens not to be very precise about what is supposed to be "nothing special, actually just standard," then two parties have found each other - at least for now until the budget question is clarified.

Have you talked to the architect about what service you expect from him ([HOAI Leistungsphase 1-2], [1-4], [1-5], [1-8]?) and what he will charge for it? If not: you should do so quickly. If I missed that: sorry.

Neighbor built the house for 610,000, acquaintance Peter for 570,000. Others had a price range from 400 to 600 thousand.
So we thought that with our maximum of 900 thousand € we would easily be in. We also don’t need a luxury house.
The money was not yet a topic of conversation.

How do you want to get offers if you are not allowed to show the plans to anyone?

Of course you are allowed to show the plans!

It would be unfair to him to pass on his documents (where he explicitly points out that they must not be given to third parties).

If you show and discuss these plans with family, acquaintances, or friends as well as advisers or experts or have them advise you, then that is not passing them on.

The prices of the other houses confuse me: shouldn’t they have prices from 2 years ago plus? They are already built. Two years ago 600,000 was very expensive! These must be elaborate villas.
And if you now plan something similar but "only" 200 sqm for 6 people, then that must be related to elaborate statics, some frills or cumulative extra costs everywhere. And you don’t see the forest for the trees – meaning the effort – because uncle or whoever has the same.
House construction has indeed increased by almost 20% in the last 3 years at least (either felt or read). It is no coincidence that everywhere things are being slimmed down and more or less many things are retrofitted (technology) and some are done in self-performance.
For example, if you plan 4 bathrooms for 6 people, that is a not insignificant part of the planning that can really become expensive. Sliding doors, exterior doors, window areas: and the second 100,000 is spent.

Have you talked to the architect about which service you expect from him (HOAI service phases 1-2, 1-4, 1-5, 1-8?) and what he will charge for it?

Apparently, this was not discussed, but an architectural contract was implied: without an agreed limitation, it then goes up to service phase 8 (because service phase 9 would be unusual for a single-family house, and it was not limited, for example, only up to service phase 4) and must be billed according to HOAI (unless agreed otherwise). "Just make us an offer first" would have been enough to prevent this. If you "withdraw beforehand" now, the architect can in substance claim to be compensated for the lost profit of the further service phases – in terms of amount, however, he would still have to specify (and explain) that. Since he deviated from the usual procedure, it will be difficult to reconstruct without protocol and partial acceptances which services were actually provided. If there is no intent to deceive, this procedure is at least highly unprofessional.