Construction costs rough estimate, realistic or not?

Isn't it sufficient to create an expert report once the excavation pit has been dug, or even to waive it if everything is fine? There are also houses on the left and right.

... if there is normal ground, no soil report is needed ...

If the neighboring property was built with a basement and there were no problems, I would forego a soil survey.

Oh, and what is "normal ground"?
How deep does the "normal ground" go?
What is beneath the "normal ground"?

we need the space for at least 4 different trash bins, bicycles, workshop, Vespa, winter tires, stroller, lawn mower, skis, tools, etc.