Prefab house expert - sensible or wasted money?

What matters is what one considers important.

If you can afford it, gladly.
If not, the ego has a problem.

The Amigo businesses still actually exist here in and around Munich. But for this, as hampshire writes, you really have to be extremely well connected. I read the place Dietersheim while skimming the topic. The area is very nice. There are many old-established residents here. Maybe have a chat with these gentlemen sometime.

And in Cologne, there is the Klüngel

Being well connected makes many things easier everywhere

If you can afford it, gladly. If not, the ego has a problem.

It's not about fulfilling all wishes, but about knowing what is important to you. Especially when resources show limits, setting priorities is helpful to make good decisions – and the assessment of what is important does not come from outside.

Those kinds of people are quacks and the best way to throw money out the window.

Such guys are quacks

In post #28 I explained why I do not share this impression in the specific case: