Cost estimate for a single-family house near Heidelberg

That can't be compared anyway. Our shell construction offers (the same service everywhere due to the scope of services) differed by 20,000 to 30,000 € at times, and this applies to all trades when building with an architect and awarding the trades individually. There is simply no standard price. If someone, regardless of whether architect or general contractor, sets a budget, they should simply build a house accordingly. And no, not just any house, but a house with one's own priorities, and then usually it is looked at what is included and what has to be omitted.

When I read your answers like this, the prevailing opinion here in the forum is that building with a [GÜ] should be cheaper than with the architect, right?

That cannot be answered that easily either. In the beginning, these are all just estimates. You would have to build dozens of houses with dozens of different architects and GCs on the same property to make a statement. Simply set a budget and see where your wishes are implemented and what kind of feeling you have with it.

Not necessarily - but it is definitely more predictable. Instead of a non-binding cost estimate, you receive a fixed price offer (for the equipment and services specified in the [Bauleistungsbeschreibung], so usually not yet for the house as it will stand later).

I can only say this much: Here in SH, GU is clearly cheaper. There are several to choose from that have efficiency and have been on the market for a long time, some of them have many trades in-house, are authorized to submit construction documents, and thus you are out of the HOAI issue. Building with GU also has advantages for companies, and our craftsmen love it: no VOB, no withholdings due to warranty, simpler handling than with an architect. Customer advantage, fixed price, and here additionally a better fixed price, as long as you stick to the GU standard. Extravagances.... then architect.

I am not sure if building with a general contractor (GU) is really (always) cheaper. Even with the standard: The GU certainly factors in enough margin/profit/risk. And as soon as you want to deviate even a little from the "usual" standard (of the GU), massive surcharges come into play. From my perspective, building with an architect does not have to be more expensive at all – you just have to allow enough planning time and time for the awarding of trades. This is probably faster with the GU (since many trades are internal). The architectural service from the GU also has to be paid for. If you do not want to build a standard off-the-shelf house anyway, it probably balances out. In times of fully booked schedules, building is less fun anyway: but this could certainly change in the next few months.