Do you live here? Because there are lots of empty lots and there are tons of under-developed areas. I don't know why you believe "Manhattan is extremely construction-friendly"; it's certainly not 'construction-friendly' enough so that there are numerous affordable housing options. Some crazy number of housing units are under either rent control or rent stabilization. The housing dynamic here is insane.
I do live here. I know of exactly one substantial empty lot in Manhattan - just south of the UN building. I still wonder what the plan is there.
Hell, the biggest development project going on right now involves building on top of a train yard. This does not suggest an availability of actual empty land.
> "and there are tons of under-developed areas"
And yes, that's precisely what I referring to when I mentioned that any new development would have to involve demolition and replacement. Replacing a 15-story apartment complex with a 45-story apartment complex may be a good idea, but first you'd have to buy out all the owners in the building.
That sort of thing is neither simple nor fast.
The infrastructure problem exists still also. Spanish Harlem can be argued to be underdeveloped - and we can surely replace those buildings with tall apartment complexes... except the 4/5/6 subway is already massively oversubscribed. You can build apartments there, but said residents won't be able to get to work. The 2nd Ave Subway is supposed to alleviate a lot of this pressure, but we all know how fast that is going.
Same goes for basically all of Upper Manhattan - there are plenty of opportunities to replace buildings, but not enough infrastructure to move people around. Transportation (like most cities) is the biggest developmental bottleneck.
> " it's certainly not 'construction-friendly' enough so that there are numerous affordable housing options."
You've missed the entire point of my post. "Construction friendliness" is not Manhattan's bottleneck. Lack of infrastructure, and systemic slowness inherent in building replacement (read: buying out existing stakeholders) are. For all intents and purposes, Manhattan is "friendly enough".
There is a building that's finally going up near me in the Lower East Side - a replacement of an old walkup. The owners in the old building resisted sale for a long time, as it would involve displacing them, plus they (rightly) speculated that their property value would continue to increase. The solution at the end of the day is to offer existing owners a brand new (albeit small) apartment in the new building. Not only did it cost the builders money to demolish and erect the new building, but also to buy out the old owners and give them part of the new property for free. Things like this are why Manhattan is replacing buildings so slowly, not because Manhattan is somehow opposed to development.
