To your last point, keep in mind that there is upward pressure on the price of single-family homes from people who want to live in a certain area but don't care

To your last point, keep in mind that there is upward pressure on the price of single-family homes from people who want to live in a certain area but don't care about having a yard or a workshop or whatever. when you build a 4-plex on a SFH plot you've gotten rid of 1 SFH but reduced the pressure on the remaining stock by up to 3 buyers.