Cost for an offer

Yes, because it is also comparable to a house
But everyone can decide that for themselves.

In what way is that not comparable?

Ever thought that a house including adjustments by the planner is significantly more complex than a car configuration? I can configure a car myself at home on the PC within a maximum of 15 minutes

I find the objection justified. The comparison is flawed due to the greater planning effort. Nevertheless, there are competitors who see this effort as a service and investment in customer acquisition. We are currently contacting these companies and are satisfied so far.

When I go to the car dealership to configure a car that I might only possibly order, the dealership also does not charge a flat fee.

In what way is that not comparable?

If you go to a car dealership and configure a specific car (e.g. VW Golf) where the catalog price is fixed by the engine power (1.0 TSI), with optional equipment, such as tires, height-adjustable driver's seat in velour look, and tinted side windows
you compare it to a fixed model house (e.g. Viebrockhaus Maxime), where the catalog price for the house size is fixed (300 with 144sqm living space), which you can configure with e.g. a better base plate, folding staircase made of oak, and foiled windows instead of white.

Both can be priced within fifteen minutes based on a catalog.

But the OP wants a house freely planned by an expert. Nothing off the shelf, individually made. That has to be designed as well as calculated.