That's exactly what it's about. If it turns out that, for these and those reasons, I can only afford to buy something for 250k after all, then I'm also one step further... But then we're going in circles again, because I don't quite understand how I can buy something for 200, 300k for x number of people who also have the challenge of children and part-time work but with less income, and here it basically turns out that even with the income we have, we obviously shouldn't and can't finance 400k in the long run.
It's not the income.
It's the doubt that you can significantly change your lifestyle. Currently, the described life motto is: "I afford this now because I want to." With a significantly higher fixed monthly burden, this will no longer be possible.
If you want to live with such a restriction, you have to consciously decide to do so, otherwise it will fail.
The families you mentioned have learned this (maybe not all of them – you might see them again at the forced auction).
So far, due to lack of necessity, you have not yet provided this proof (otherwise you would have saved something and not spent everything).
Hence the constant reference to the household budget book. This shows you best whether you can manage it over a longer period (9-12 months) and where the money goes. However, statements from you like "keeping a household budget book is too exhausting for me" (something like this was said somewhere once) cast doubt on the seriousness.
Others build and invest a huge amount of their own work and thus save parts of the investment. I admire several of my neighbors for their courage and skill in doing so.