@straffrei where do you get the information that the house above is overpriced? I think there is already a huge difference in the insulation alone. Schwörerhaus also includes a heat pump as standard, etc. I think you can't say that based on the information given.
Regarding the budget, I can only fully agree, that won't work out. For the ancillary building costs, you have to include property tax and notary fees, then the construction ancillary costs such as earthworks, sewage, construction water and construction electricity, then you probably need furniture etc.--
I'm pretty deep into the subject right now and can definitely say that what you claim is wrong. Schwörerhaus does NOT have a heat pump but a ventilation system with heat recovery that heats with electricity at cold temperatures. Furthermore, Schwörerhaus has a poor standard basement. That is why the staircase from the basement is completely closed off and not open. Otherwise, too much cold comes from the basement. Furthermore, Schwörerhaus is plastered directly in the factory, which results in heavy use of silicone at the corners where the walls meet. What I personally don't like is their vapor barrier. You can clearly see from the outside where the ceiling runs. It's hard to explain.
So, I've been with many providers by now, and at first, I was a total Schwörerhaus fan. But meanwhile, I had to admit that they are simply not the best in quality. Price-wise, of course, they are great. Meanwhile, I'm paying about €20,000 more but, in my opinion, I also get much more. For example, a proper air heat pump and a ventilation system with heat recovery, wall heating, a basement with a white tank (water- and earthquake-proof) and a dormer...
Oh yes, both houses are KfW 70 and have the same insulation. Only the basement at Schwörerhaus is poorly insulated.