Additional positions in house construction: are they useful and reasonably priced?

Is €17,300 really cheap for a central ventilation system? It’s about a Zehnder system. For me, with 162m2 living space without a basement, that really seems expensive...

Surcharge for central ventilation system with heat recovery Zehnder from us 11400 euros. Slightly less living space than you. Without basement.

The offer was from January of this year. Additional charge compared to window rebate.

Gross or net?
Thanks for the information

but to some extent we still need to upgrade the electrical system a bit. For example, more sockets, spotlights, lights with motion detectors on the stair steps, spotlights in the roof overhang, etc.

But we wanted to upgrade that directly with the specialist trade and not through the general contractor