150 Euro / sqm development costs = realistic or usury?

The development is already complete.

I can only partially understand the large differences in development. With us, the plot costs 98€/sqm fully developed. In Markelfingen, 20km away, the development alone costs 120€/sqm. This certainly cannot be explained by wage differences.

That also depends on the area. What needs to be addressed? What might already be prepared? For example, does the canal need to be enlarged due to the new properties, is an additional sewage treatment plant required, etc.

The companies from NRW will be pleased, as it is well known that there is a shortage of construction here and they are already eager for the orders from Munich to finally arrive ;-)

From the said source (or is the source lying?)

Yep, the source did not present it correctly. This is not the development of an entire residential area. I have already written this several times - but you simply do not want to understand it (addition: If you get bored sometime, you can also look it up in the Building Code. I particularly refer to § 127. If the municipality has to buy land for, for example, roads and it costs more than €1,000 per square meter, it will be a really expensive road...)

P.S. I just looked it up again. 100% of the costs for you are also legally okay - if a) there is a development contract between the city and an investor or b) there is a project-related development plan. So don’t sue right away but first get informed.

I assume that was meant rather ironically. :/ Ok, but that there is a construction boom in the East, away from the big cities, would be news to me. And there will surely be companies there that can develop plots of land, right?

Anyway, with "us," the actual work is pretty much done. Who knows, maybe we can talk some sense into the one council member we know personally to be really "socially responsible" (as constantly promoted by the municipality) and convince them to cover most of the enormous development costs. Well... I don’t really believe in it, but it would be dumb not to try.