Surcharge for subsequent sampling, discount for withdrawal

To stick with the car example, if I now choose a car color that is not a standard paint but a super special metallic paint, it is quite clear that I pay the extra charge. But the car dealer does not just look at the car and say: "oh, nice color, I would like 25% more for that"

It doesn’t have to be a super special paint or metallic. Even switching from solid white to solid blue can be expensive. Ultimately, the discussion is pointless. Your contractual partner is not the subcontractor who actually installs the front door. Your contractual partner is the general contractor and you have a construction performance description as part of the contract for front door X. It was your task to consider before signing whether you wanted it or not. And if you wanted a different one (we are not talking about color here, but comparing a Golf and a Mercedes), the right time would have been during the offer phase to include the corresponding door in the construction description. Now you want front door Y and for that the general contractor can practically charge any price, regardless of what that other front door costs him. That is why it is so important that a general contractor’s standard matches their own desired level as closely as possible. Upgrades of any kind are always significantly more expensive than the actual additional costs. During the offer phase you could still have easily chosen another general contractor...

I would recommend trying to completely outsource the staircase and front door and contract them externally. The subcontractors of the general contractors often charge exorbitant prices because they know the clients are not able to approach other companies. Especially for the staircase, I would suggest contacting the local metalworker. We also completely outsourced the staircase because they wanted a 28,000 EUR surcharge for the model we wanted. Now we are contracting directly with a local provider and are only paying 14,000 EUR for the colored steel stringer staircase with a 14m all-glass railing.

What was much more surprising, however, was that it says there that if you make any changes, you have to pay an additional 25% on the difference as a "business cost surcharge".

With our developer, I think it's 20% (I would have to check again, but it was either 20 or 25 - but I believe 20) and I think it was even stated like that in the contract. So yes, I'm initially also at "not uncommon". For some things I think, yeah, they still have to replan something or the like, but for others it seemed exaggerated. But that way it's done in one go and you don't have to coordinate the trades yourself or anything. However, we didn't have any individual items that were that expensive.

Hello,
Remove stairs and front door and find someone yourself, then you have more options, more offers, and no annoying general contractor. But the +- 30k for 2x folded structure and glass... That is already realistic.
Best to also remove parquet and painting work right away – it doesn’t sound to me like you will take the standard general contractor 30 euro parquet and the coarse-grained spray plaster...
Tuition fee the 15% and after that you are "free" with these things.
GD