Those numbers are probably accurate. The reason it doesn't add up to you is that you aren't thinking about the actual costs of residential conversion or the ma

Those numbers are probably accurate. The reason it doesn't add up to you is that you aren't thinking about the actual costs of residential conversion or the math behind $100/sqft. The easy one: $100/sqft isn't $100/sqft for each apartment, it's $100/sqft of building. That means that you have to count hallways, lobbies, elevator shafts, mechanical spaces, internal walls, etc. All that adds up. The hard one: The $1000/sqft conversion cost. This comes down to the fact that residential and commercial buildings have very different floorplans. Commercial buildings keep the plumbing near the elevator shafts because it's more efficient, but residential buildings need much more extensive plumbing on each floor to give everyone a bathroom and a kitchen. Electrical metering and wiring also becomes a lot more complicated. You also have to do things like putting up walls and light fixtures (usually commercial tenants pay for that in the spaces they rent) and installing residential appliances. All of that adds up to a quite significant cost in a place like San Francisco, notwithstanding the costs for permits.