And online forums

The average also includes the €50k one-room condominium. After all, not only palaces are traded.

As for the 8% interest on full financing, I think something else is meant there. Namely that the last 5% or 10% (i.e. instead of 90% or 95% financing, it's 100%) causes such a jump in conditions that you end up with 8% interest on that portion...
Here's an example, 90% at 1.5% interest, 100% at 2% interest, €100k total (completely fictitious). That means this 10% causes a 0.5% higher rate on everything; if you now apply the old interest rates to the first 90% (1350€/a), then the remaining 10% costs 6.5% interest (2000€ - 1350€, i.e. 650€ for €10k). For that, you could almost take out an installment loan to reduce the loan-to-value ratio... which is occasionally offered as well.

so here specifically new construction I only read the extreme cases.....

+/- 100 k depending on the region

so here especially new construction I only read the extreme cases..... +/- 100 k depending on the region

This is a filter bubble. The thing is called HOUSE CONSTRUCTION forum after all Besides house there are also ETW and besides construction also existing buildings. But the new construction of a house is the most expensive option. And then there are the buddies who build a two-family house pro forma because of KFW subsidies, where the office formally becomes a granny flat and thus from the 500 TE loan mathematically 250 TE per object...

It's logical after all. Why would someone who is sure about the financing and can easily manage it report in the financing forum? Usually, only those who are relatively tight report there. You won't find [Bauherren die 250.000€ Kredit bei 5.000€ Netto] there. Almost exclusively, only the extreme cases report there. Regards

It may be that I am completely wrong, but:

Are you sure that the loan amount is considered per construction project and not per borrower? 248K on average seems rather low to me....

€: The article also mentions that Germans had to go into debt to this extent on average and not that this amount was borrowed on average per construction project.