Wow, at almost $600/sf, these appear to be bubble prices to me. At these lofty levels, where is the catalyst for the upside going to come from...does anyone believe these will be trading at $800/sf in a few years...especially when rates will likely be higher and loads of new units will come online?
Consider that units along Central Park in NYC trade at "only" $1000/sf. This may add some perspective to the pricing.
Honestly, I think the non-speculative people buying here (probably mostly doctors, lawyers, bankers) consider losing a hundred grand or so a rounding error on their net worth statements, so the ability to have marble floor bathrooms easily outweighs a potential market downturn.