Construction costs are currently skyrocketing

If prices recover, will this also be passed on to the customer?

I doubt that somehow. Rent something now and build in two years? Who seriously thinks it will be cheaper then?

Once the price level has settled, nothing goes back. Or has anyone ever experienced being called by their general contractor after signing and waiving the right of withdrawal, saying it will be cheaper because the material has since become cheaper?

Living in a single-family house will become a privilege of the upper middle class in the medium term. It's that simple. Whoever can, should try to build/buy now. Waiting means never becoming a single-family house-buying person. Those who wait for the bubble can wait for a very, very long time.

Once the price level has settled, nothing goes back anymore. Or has anyone ever experienced being called by their general contractor after signing and waiver of the right of withdrawal, saying it will be cheaper because the material has since become cheaper?

Yes, I have ;). After the contract and signature and then after completion of the shell construction, the invoice was about 10K lower than offered.

Yes, me ;). According to the contract and signature, and then after completion of the shell, the invoice was about 10K lower than offered

Then the general contractor probably just miscalculated in the original offer :-)