The higher up, the better view, and more proximate to parking and transportation, the price per sq ft will increase.

Right now, about $560. A bit more if it has a full-on NYC view.

Depends on area/building, actual condition,floor, end unit next to the elevator etc...
I've seen the range from 1000sqft to 1300sqft-- 500K to 800K and vice versa. Need to look at local comps once you see something you like... I'm local, if in fact you want a Realtor to see you through it - I can go over the comps..