Construction is expensive but at least not difficult. Entitlement and permitting are the real nightmare here. It's why we basically don't build anything.
what about the massive amount of housing starts that dropped off after the financial crisis and took a while to recover, and never got back to the same level? that seems like a big part of the problem too. https://fred.stlouisfed.org/series/HOUST
The article is about California and I would suspect that relatively few entitled projects are abandoned there. If you know where to get the relevant data, please share.