Price difference oak staircase oiled or lacquered

Which circumstance should make the 1700 euros comprehensible?

There is certainly a certain degree of profit intent involved. To be fair, one can also consider that any deviation from the standard causes additional costs, especially since a prefabricated house is partly a kind of serial product. So you cannot simply compare the price of a freely requested painted staircase with a freely requested oiled one. This is just a side note; I do not want to evaluate the specific figures with it.

There is certainly to some extent an intention to make a profit. To be fair, one can also consider that any deviation from the standard causes additional costs, especially since a prefabricated house is partly a kind of serial product. You cannot simply compare the price of a freely requested painted staircase with a freely requested oiled one.

Just as a side note, I do not want to evaluate the specific figures with this.

The prefabricated house is designed entirely according to my wishes. There is no serial product. Every staircase is different.

As with many extras, this is the eat or die method. It's no different with cars. S line on the Audi? 2500€ extra, even though only a different bumper is screwed on and the actual price difference is very likely between 0 and 10€. Or underfloor heating, where you pay about 4000€ more for a 30sqm house depending on the region. Material and labor are similar compared to normal radiators.