Hm, then how all this plays out for landlords? Lower cost of capital (relative to mortgage)? Cheaper upkeep due to economy of scales? Nah, those differences are probably too small.

How would you compare the cost of buying a house vs. building one? That might be the answer. Here in Croatia it is not uncommon that gross margin for builders who sell new houses (or, more often, condos) runs as high as 40%. (The price for a decent new condo, unfurnished but with central heating (rarely air-conditioning) and bathroom fixtures, is typically $120-$150 per square foot.)