But this is all at the very high end -- you see in manhattan that houses people actually live in sell at half the $/f2 that unused "investment" properties do.

But this is all at the very high end -- you see in manhattan that houses people actually live in sell at half the $/f2 that unused "investment" properties do. I suspect that the discrepancy in the $/sqft ranges is more about the property quality and scarcity at that range; you pay a premium for an 8,000 sq. foot duplex with a terrace that overlooks central park and has world-class finishes and amenities because there are far fewer of them than ultra-wealthy people who want them.