Interesting semi-tangent: so I recently moved from the states to Munich, and I live in a little apartment complex in a low-ish density neighborhood (Solln) that has 10 units. Somehow, this place has underground parking, which was initially shocking to me, because I don't think I've ever seen such a small apartment complex in the states with that; usually you'd only seen underground parking in far larger complexes in the middle of a downtown-type area.
And my complex isn't unique, tons of small buildings here seem to have underground parking. So maybe it's not that expensive when it's a common thing to do.
Might also just be a side effect of Munich being one of the highest quality-of-living cities in the world, with some pretty high-end auto manufacturing as well.