It's supply and demand. More available housing means lower prices.
Does it? I don't understand this, at all.
More available housing would also create more demand, no? More people online will see the lower prices and move to Manhattan, immediately increasing the price again, no? The situation is complicated. You can't just say "supply and demand" and think you've solved NYC's problems in housing.
ECON textbooks teaching students that every person is a financially rational actor and that supply + demand plays out real nice in the real world is supper dangerous. My econ textbook was wrong in a lot of ways and it's upsetting to see continuing oversimplification and massive condescension for these antiquated and not-real-world-tested perspectives on how to solve complicated urban problems.
By that logic, I could build a massive apartment tower in the middle of nowhere and people would flock to live there. China tried that - it didn't work.
https://www.businessinsider.com/these-chinese-cities-are-gho...
Housing is a market just like anything else. In any market, if the price gets too high, competitors jump in to create more supply to meet the demand. If apples were $100 a piece, everyone would grow apple trees in their backyard and make a fortune until the prices came back down to a reasonable level.
So why aren't developers pumping out cheap apartment buildings left and right? Why aren't they buying empty parcels of land and putting up massive towers? Because they can't. Because local zoning laws won't allow them to.