Just thought that I'd share a little known fact about house, coop and condo sale prices: they're public in NYC. The City's Department of Finance keeps a rolling file of all closings in the 5 boroughs. The sales are separated by borough and year (all the way back to 2005!). Right now the sales are only current as of Aug 1, but that's not too shabby.
If you download the excel file version, it is very easy to find what you need. Hit Ctrl +F to run a "Find" search within in the document, or just click on the Edit tab up top and pick Find.
Here's the link, just scroll down a bit when you get there: Happy Real Estate Price Voyeurism!
Have fun! You're Welcome...