100$ a month is probably on the low end. A parking spot is at least eight square meters, probably more like nine. Rent here in Berlin is about 10€/m^2/month (so pretty cheap as far as big cities go). Typical houses have three to four stories, so that parking spot could be 24-36m^2 of housing.
My apartment building has a central garage with a place you can charge your car (probably) for free. Unfortunately someone (out of a few hundred) is already using it.
