Construction costs are currently skyrocketing

That may be true, but for that you need an electrician who then makes the connection on that basis and still offers a warranty. Many don't do that.

My experience: Most do that. Even very gladly, because it is easy money.
I prefer to take care of the big construction sites and quickly grab the money on the single-family house ;)

Yes, I would think so too, but actually my experience is exactly the opposite. Maybe it's also a big city thing.

Ok, for the electrical inspection, yes. For that you need Wilhelm from the master, but what is not doable by yourself in plumbing? The house connection outside the property? Back then I called the city because I thought it would be a good idea to check/renew the 100-year-old sewage pipes, and the city said they do it themselves and also decide themselves when it is done. I wouldn’t have been able to renew it (have it done), which I found strange.

Everything related to drinking water requires a registered master craftsman with us in Berlin.

Ok for the electricity the approval, yes. For that you need Wilhelm from the master, but what is not doable by yourself for plumbing?

For the electricity you need the approval and usually you can find someone with whom you can contribute your own work. For some maybe even everything by yourself and he only checks – but usually they at least want to clamp the wires onto the rails – which very few builders can do themselves.

Similar for plumbing. Heat pumps only work with a refrigeration certificate (of course Monoblock / Hydrosplit works without) and depending on the region, you are not allowed to lay water pipes yourself or the insurance will ask who did it if something goes wrong.

You are allowed many things, but who can do: electrical planning and execution, plumbing/heating planning (including heat load calculation and installation plan) and execution, floor constructions, plastering, drywall, tiling, window construction, carpentry work all by one person or within one family? That might be 2-3% of builders who can do that themselves or dare to try. You can’t expect that, especially with today’s demands on technology, equipment, and perfection of some builders.

I had to present the pressure test from the specialist company for the wastewater, otherwise I wouldn’t have gotten a drinking water meter. And the municipal utility technician won’t install a meter for you if there is no approval of the installation.

If an electrician signs off on it unchecked, fine. Since the house installation ultimately concerns my property (keyword fire) and my life (keyword poorly executed PE), I would not let it be signed off without a proper acceptance...

A leaky KG pipe connection is found by pressure testing, a defective PE by measurement. Not otherwise. The damage can amount to thousands... if the daughter lies dead next to her defective CD player because dad forgot to connect the PE and wanted to save the measurement, it’s priceless...

PS: I’ve already seen more than one loose PE in my life... fortunately “only” in industry, before handover to the customer...