ᐅ Is the price for a precast concrete garage reasonable?

No, but it has to look exactly like the plan later on.
I already posted this in another thread. The garage must be fully clad with wood.

A timber frame might be an option, but the lower part of the garage will be backfilled with soil. I’m not sure if that will work then.

Then there is still the suggestion of a "carport." Having it built as a special feature by the local carpenter is more common than trying to achieve this with precast concrete elements. In addition, the wooden cladding is included directly. However, I would lean towards steel because of the green roof; with wood, the material would become very thick and expensive.

Earth-covered... wood probably wouldn’t work, right? How about supporting it with L-shaped blocks or placing a carport/whatever on top?

In the end, there will be a masonry garage with the associated costs. Or, of course, none at all.

I sent the plans to various suppliers. Now the price is just under 36,000, no longer 50,000.

If it goes down further, that would be great.

Having the walls built with masonry will be far too expensive. Also, you lose interior space due to the thicker walls. This isn’t ideal given the narrow driveway.

By the way, the masonry option was at 54,000.