Construction costs and financing for apartment or house

No, that is untrue. Solid oak floorboards are among the highest quality floor coverings you can get. And the material price for the wood is indeed in that range. However, several work steps are necessary for the installation: preparing the floor, gluing it fully, sanding (multiple times), and oiling/varnishing/waxing (possibly multiple times). That makes the whole process very expensive. I can't imagine you can manage with a double-digit amount per square meter overall.
Solid floorboards are made to last forever.