There's a significant price differentiation between living in Manhattan and in other boroughs. One really can't lump them all together.
I have friends that pay $6-700/mo for rooms in reasonable apartments in convenient locations in Brooklyn (e.g. off the Lorimer L stop, less than 10 mins from Union Square). Rents have also significantly gone down in NYC in the past two years. I had mine decreased by 12% last year and it hasn't gone up since.