I really don't want to discuss construction costs here, only floor plans.
In our last construction project, I received exactly the same resistance regarding "that just won't work." Ultimately, what matters is only what is stated in my contracts, what comes out of my account, and what the result is. And contrary to all the pessimism (even back then, without the increased costs), I have a house standing here. At the costs for which everyone back then called me naive. I'm sitting inside, it is heated, it exists.
There are simply regional differences in construction costs. I am not seeking any assistance regarding the cost side of this project. I swear solemnly not to complain about our insolvency either, should I have miscalculated. :P