Level the basement or the plot?

I can give you a few prices from 2017.

We had to do soil replacement under the floor slab of our basement. Our earthworks contractor charged 22.50 EURO net per tonne of KFT including travel and installation.

If I understood correctly, your architect only wants to fill the floor slab, driveway, garage, and terrace with KFT. I think the estimated 80 EURO per cbm is more than cautiously calculated.

For the garden, I would talk to the builder; they are happy if they can "dispose" of their excavation material from their construction sites cheaply. Usually, you don’t pay anything here.
Of course, you have to fill the top layer of 20-30 cm with good topsoil, but below that Z0 soil is fine.

If I understood correctly, your architect only wants to have the slab, driveway, garage, and terrace filled with KFT. I think the 80 EURO per cbm set is more than cautiously estimated.

Exactly, you understood that correctly. The rest would be filled with excavation from other construction sites.

Exactly, you understood that correctly. The rest would be filled with excavated material from other construction sites.

And that costs you almost nothing if you do it cleverly. For example, a earthworks contractor here always advertised in the newspaper that he would fill plots for free.

Excavation itself doesn't cost anything here either. It is simply dumped for you. Costs for grading apply. When the house is standing, will a truck still come to the rear area? Easily accessible. One company refused to deliver to us. It was too tight for the driver.

Bringing the house to street level is also more of a wish for us to ensure a nice appearance.

A nice appearance is created with optical means, not technical ones. It’s not as if the ground floor would look like a basement without filling here.

Nice appearance is achieved by optical means, not technical ones. It's not as if the ground floor would look like a basement without filling.

Rather? Single-family houses below street level look odd!