Affordable providers for building a move-in ready house

Paving work, carport etc. is of course also your business and has nothing to do with the house construction company. However, they will also arrange that for you for shiny euros, even the moving service. But you can certainly get all that cheaper if you "take care" of it yourself.

I am only interested in the experiences that perhaps some have already had exactly in this price range. Thanks :)

When should these experiences have been made? I built 10 years ago. Back then, that might still have been a realistic question. Not anymore today.

A prefabricated house is offered without a foundation slab.

That is not generally true. Town & Country offers its houses including the foundation slab.
The Flair 110 in our area for 234,000 euros, it can be different elsewhere.

In addition, there are ancillary building costs including connection costs (which can vary greatly), but I would plan at least 20,000-30,000. Unfortunately, the earthworks are poorly predictable beforehand, and 10,000 euros can quickly be added. Even a soil survey only offers limited security.

When selecting fittings, you have to be very economical. So initially a cheap toilet will go in, which can be replaced quickly later.
For the electrical work, you have to expect additional costs; you will want a few extra sockets.

I would then look for painters and floor layers on the portal with the hammer. If you have time and not so much money but prefer to do it yourself. It’s also fun to accomplish something.

That is not generally true. Town & Country offers its houses including the foundation slab.

Town & Country is not a prefabricated house, but builds solidly.

Town & Country is not a prefabricated house, but builds solidly.

You are absolutely right. However, I think OP used the term prefabricated house in the sense of a house planned and built from a single source.

I'll keep it short. Since one is supposed to disregard remarks like unrealistic, here is my realistic answer.

There is no move-in ready.