Feasibility Single-family house + land 400,000 €

As mentioned, these should be examples to think about whether something is really necessary.

For two of the twelve points mentioned, most people now probably agree that they cannot/will not do without them.

And it was not about what I would be willing to do without if I were to build or at what point I myself say that I would rather stop altogether.

Basically, it doesn't matter to the OP and it's just my opinion. But I never wanted to have a house just to live in. Especially not when the feeling accompanies me for 20-30 years. I can also have that experience as a tenant. Especially if I have to lay down 450k€ and not get what I actually want. Laying down 450k€ and possibly not getting what you want is out of the question for me. You have to pay off the house for far too long. It was important to me to build a house where I come home every day and am happy that the house turned out the way I wanted it. That simply makes you happy. For that, I am happy to pay 100k€ more. It would have been great if I could have built the same house for less. But that wasn’t the case.

On the other hand, when it comes to a home that accompanies you for half your life, you are also more willing to do some things later or actually constantly tinker with and improve it. Of course, it's also a matter of personality whether you do that at all. But when I think back to my rental time, I actually never felt like painting a wall or even replacing the floor before moving out, in other words, increasing the living value of someone else’s property just because I happened to live there. It's quite different with a home you own. But I definitely believe that people easily underestimate the work and costs involved in building a (new) house, or at least I'm experiencing that firsthand right now.

Above all when I have to lay down 450k€ and don’t get what I actually want.

That is, of course, also a question of personality, whether you do it at all.

Oh yes, the personality question. There are people, myself included, who are very flexible. At the end of the day, I don’t care at all whether the tiles are 20x30, 30x60 or even larger, and what color and pattern the things have. I find many very differently designed bathrooms beautiful, so I can just decide on any variant. The extreme opposite are people who are afraid before every decision that they might regret it for 30 years. You only build once, it has to be perfect, plus the mentioned expectation to want everything perfect for sum x. And woe betide if the joint is stone gray instead of silver gray, that would be the end of the world.

I also believe that no one has to earn 100k€ as the main earner to afford a little house, but anything over 400k€ in loans should require a net household income of 5500€ to be able to sleep peacefully with children.

Basically, I agree with you, but I think you can make an exception here. You really can't get more security than two civil servants, and if they are willing to make sacrifices, why not.

The extreme opposite are people who are afraid before every decision that they might regret it for 30 years. You only build once, it has to be perfect, plus the mentioned expectation to have everything perfect for sum x. And woe betide if the grout is stone gray instead of silver gray, that would be the end of the world.

Those exist too. You can make life difficult for yourself or the woman makes it difficult for you or both amplify each other. We didn’t have any of that!