How much does a mostly self-built house cost?

I think that since the craftsmen give 5 years of "warranty" on a house, there must be markups built in somewhere. With self-performance, you have 2 years of warranty, but only on the part, not on installation, etc. (and check after 1 year, for example, that the error in the exchanger was not due to incorrect installation)..

What do I not understand here? It is about the savings on EL in relation to an hour of a craftsman - not what remains with the craftsman or what it costs the entrepreneur.

I never wrote anywhere that you don't understand something. The example is only for illustration.

I never wrote anywhere that you don’t understand something. The example is only for illustration.

The question was not directed at you.
Nevertheless, you are currently off topic.

I would also not rely too much on friends and acquaintances always having time. I had the experience with a colleague who had built a shell house with an Allkauf Haus and did everything himself. We had agreed that I would help him occasionally (which I did about 10 times for tasks that are difficult to do alone or when there was time pressure) and that he would later help with my build. Not once did I see him at my place. I asked twice if he had time, he (allegedly) didn’t, then I told him once more that he should let me know if he ever had time, and until today (over a period of 2 years) he apparently still hasn’t had time...

Have you ever told him that he is an a**hole?