Surcharge for WU concrete basement

With us, the soil survey revealed that we should waterproof our basement against ground water pressure. The additional cost we have now been quoted for this is quite significant. What additional cost compared to a normal basement is typical for something like this per square meter?

regionally very different I can't give you a comparison, but I can advise you to simply contact 10-20 companies and ask for an offer for WU Keller (with exactly the same equipment as your provider) then you will have a real assessment from your area whom you then build with is still up to you

Why was the offer so much more expensive?
How large is your floor area?

So the base area is 140 sqm and the wall area that goes into the ground is about 110 sqm. The surcharge for that is 25,000 EUR. So it almost knocked me off my chair.

Against a masonry basement or concrete?
A white tank would be around 23,000 more expensive for us than masonry, calculated on 100sqm floor area without exterior walls.
I can recommend you to ask a basement builder. You might get a better offer there.

If the surcharge is for [gemauert] and takes the size into account, I don't find that too excessive either