Construction costs are currently skyrocketing

So during my rental period I did not receive an invoice for this, the items were largely covered by the cold rent, since the cold rent already includes corresponding advance payments.

I think you are mixing things up a bit. You paid a total rent to your former landlord. This includes the cold rent (= basic rent) and the apportionable additional costs (= operating and ancillary costs). For the latter, an advance payment is made to the landlord. In addition, there are also electricity, internet/TV, and sometimes gas. These items also count as ancillary costs, even if the landlord has nothing to do with them. All of this is then the famous and very vague (because often defined differently) "warm rent."

Yes sorry, you are of course right, I also wanted to change to the warm rent, but I overdid it. :)
Still, the chances are probably high that when calculating the equity and the ancillary purchase costs over 32 years, the example of [Fichtenwalde] with the mentioned figures per rent holds true.
But the mostly higher living comfort and the associated feeling of life is allowed to cost something.
As said, overall hard to compare. Almost everyone in my colleagues has built in the surrounding area, comparisons are often made with Berlin prices. By the way, the most is then complained about the commute to [Berlin Mitte] (train is crappy, car is so expensive) and with the political outlooks the problem is currently getting even bigger.

I can gladly calculate a 1% increase p.a. in rent. But then the calculation clearly favors homeownership even more.

I doubt that. Please don’t forget the opportunity and consideration of investing the equity and the maintenance reserve. With 100k equity, 140€/month savings (fictional maintenance reserve), and 3% annual return, you end up with well over 320k. In addition, there are usually lower additional costs with a rented property, where the difference can be invested accordingly. It is simply not SO clearly better to buy. Not to forget the many small amounts that constantly flow into the house and garden without being taken into account.

I doubt it. Please don't forget the possibility and consideration of investing equity capital and the maintenance reserve. With 100k equity capital, €140/month savings deposits (fictional maintenance reserve), and 3% annual yield, you end up with well over 320k. Usually, there are lower additional costs with a rented property, where the difference can be invested accordingly. It is simply not SO clearly better to buy. Not to forget the many small amounts that constantly flow into the house and garden without being taken into account.

I would rather say that the additional costs for a rented house are higher than the additional costs for equity capital. Keyword: administrative allocation, maintenance reserve, etc.

Is this really just a question of money for you?

What do you do in a rented house when ...
- design wishes in the bathroom (different tiles)
- change requests in the floor plan (prefer a closed kitchen after 10 years)
- desire for a conservatory
- desire for a swimming pond in the garden
- ... and termination for personal use after everything is finally nice?

The freedoms and planning security that you have as an owner should definitely be taken into account in the calculation... or for many (like me) cannot be compensated with money.

Is it really just a question of money for you?

What do you do in a rented house when...
- You want to change the bathroom (different tiles)
- You want to change the floor plan (actually prefer a closed kitchen after 10 years)
- You want a conservatory
- You want a natural swimming pond in the garden
- ... and a termination for own use after everything is finally nice?

The freedoms and planning security you have as an owner should definitely be taken into account in the calculation... or for many (like me) cannot be compensated with money.

No, it is not. Otherwise, I wouldn’t own property. I just want to counter the mindset that owner-occupied property is economically such a great deal.

I really value my house and land. But it is a luxury to own and also design something so expensive.