Construction costs are currently skyrocketing

And after how many years is it paid off? And how high will the reserves be by then?

Probably until retirement, and since it is a new building, you don't really need substantial amounts for the first 20 years. Where is the problem?

expensive. Then the decision for ownership is not a financial one but an emotional one.

For many, it is then a purely financial decision: rent = lost forever; annuity = at some point, it belongs to me as a fixed asset.

Probably until retirement and since it is a new building, you don’t really need significant amounts for the first 20 years. Where is the problem

The problem is the naive approach. You can get good information about full cost calculations (among other places, here in the forum). This does not need to be elaborated further in this thread. Just a note: Renting is usually cheaper. If it is "clearly different," the calculation is wrong.

Here is a good example:

Rent = lost forever; annuity = eventually I own it as a fixed asset.

And after how many years is it paid off? And how high are the reserves by then?

Who cares? I don't want to live by "When is it paid off," but to have a good life. And that costs either a €1,650 installment or possibly €1,650 rent. I choose the installment and don't care about what remaining debt is left at retirement, because the installment will ALWAYS be less than rent. In the end, the homeowner wins (at least the vast majority, some renters do save for old age after all – but forced savings through ownership is significantly more effective than giving in to the temptation to simply squander ongoing surpluses).

I don't want to aim for "When is it paid off living," but to have a beautiful life.

"No risk, no fun" is an absolutely valid life motto. And I don't mean that ironically. :)

The problem is the naive approach.

No, the problem is that in a forum many people see their own knowledge (or maybe it’s an opinion) as ultimate, or at least present it that way.

Regarding your opinion that renting is cheaper, there are just as many other opinions.
Will the rent still be the same in 20 years? And what about the installment for the mortgage?
Or I’ll ask my acquaintance who received a notice of termination due to personal use two weeks ago. She has to move out in 3 months and has to quickly find a new (affordable) rental apartment with 2 children. I wouldn’t be up for that... I’d rather do it like
There are pros and cons to both. In terms of numbers and soft factors.

Your closing remark that this doesn’t belong in the thread doesn’t make it any more correct.

The original question was why so much is being built today compared to 25 years ago. Since this relates to the question of construction costs.
Whether the calculation behind it is correct or not is completely irrelevant here. If many people conclude that they prefer to become homeowners rather than rent, if the rent were exactly as high as the installment, then that is a factor.