Construction costs are currently skyrocketing

If ETICS, then also consistently with the thinnest possible wall behind it (isn't 17 cm sand-lime brick even enough?). Otherwise you combine the disadvantages of both systems

No, because sand-lime brick itself has no insulating effect and bricks are easier to work with.
You combine the disadvantages of both systems in any case, yes.

I have exterior walls 17.5 cm sand-lime brick (inner wall also sand-lime brick) and 20 cm mineral wool.
What mistake did I make in choosing the building materials?
Please report from your own experience in the answers.

Read his statement in the context of the discussion.
It was not about you and your choice of building materials, but about the wall structure that Town & Country seems to prefer offering and the possible reasons for it.

thank you for your post
https://www.hausbau-forum.de/threads/baukosten-gehen-aktuell-durch-die-decke.38976/post-600612

I have always wondered about such a question regarding the price differences. I am also in your league with Heinz von Heiden. And I have absolutely no complaints. I don’t need golden faucets or anything like that.

Personally, I would prefer sand-lime brick, mineral wool plus clinker facade. It is the most expensive option but offers the best sound insulation, heat protection, and durability. The disadvantages should be known. The "budget companies" build the cheapest option. It is also load-bearing, works, you can live in it, hang pictures...

I quickly glanced at that one thread; 2 full floors plus a basement just above the groundwater level will certainly drive up the price even without luxury fittings

For us, the price drivers are, for example, the living area, details of the cubature (expensive reinforced concrete work), large aluminum window areas, the number of skylights, and the double-shell masonry. What is also really expensive – we decided against it – would have been a basement with a waterproof concrete shell and a massive double garage. Inside, you can spend quite a lot of money on electrical (KNX) and sanitary installations. Higher-quality flooring and painting work are not as expensive compared to the structural work, and they can relatively easily be redone even years later. In building technology, the price can also be driven up with higher-quality products.

We would have also needed a white tank. Additionally, possibly natural arsenic (not harmful for the garden, but must be disposed of as hazardous waste instead of soil) and the basement was financially severely strained. Whether you really redo the floor coverings again after a few years... I don't know. We considered the options (keyword child) as well, but that also means spending double the money.

What I also found interesting... both with the tiles and the sanitary equipment we basically always stayed within the range of the cheapest options the dealer had on display. Still, I find the almost 9000€ for both bathrooms quite expensive and 38€/sqm for 30x60 tiles not necessarily cheap. At least with the tiles, the dealer can keep up quite well with internet prices, so that's probably not the reason.

Sorry, I haven't checked yet and don't have it in mind, but I had to raise my eyebrows a bit at the combo??? What heating load do you have and how did the plumber come up with installing such a wreck?

I have to honestly admit that I have not seen a concrete heating load calculation for our house yet, but the heating energy demand should be around 20 kWh/sqm per year according to the general contractor. Roughly estimated, that's about 4,700 kWh per year. I had already asked him the question whether the ALM 4-12 isn't somewhat "over the top." You can probably guess the answer. To my shame, I have to admit that I didn't read into the topic deeply enough in time. Meanwhile, the heat pump is ordered and on its way. I can't do much about it anymore. :-/ In hindsight, I should have taken the smaller device, the ALM 2-8.