Well, I have an 1,800 square foot loft for rent in Chelsea for $1,800 and another loft in Chelsea that is 1,000 square feet for $1,500. So I guess $1.00 -$1.50. There are crappy apartments for as low as 60 cents, however you get what you pay for. Lofts always rent for more because of the high ceilings, exposed brick and open concept.
Hello Hornster- This is a tough question. The average may have not much to do with the place you have in mind. If the avg. is $1.20/ sf for the whole city, then you could have an apartment in Chelsea renting at 60 cents/ SF and others at $2.00/ sf.... Just keep that in mind for whatever you're analyzing.
If you need more help, feel free to contact me sometime. Thanks, and good luck,