If you really get the property for 75 T€, that should be possible - maybe at first only one parking space and then the garage or the kitchen for 10 T€ and not for 20 T€.
We are also currently planning. The offer from the prefab house provider is available. (Stadtvilla total 240sqm, of which 80sqm is a separate apartment on the ground floor). We are currently waiting for the offer for the corresponding solid house. We already have the builder's assurance that he can definitely do it for the same price, possibly around 10,000 cheaper. But with better equipment. In addition, the solid house provider is significantly more flexible. Especially when it comes to the interior fittings.
If the price per sqm for the land is really only around €100-150... We come up with about €230,000 for a solid house, but there are hardly any special requests included, just a few small things. So the total of €400,000 is really tight. Our plot is about €20,000 more expensive. In total, we are calculating with €450,000-475,000.
If one is mean, one could say that you only have to be flexible when the planning is wrong
But well, that's certainly true.
However, for some system house providers as well as in solid construction, the variability is very limited.