Here's an unscientific little chart.
I made a list of a handful of buildings in Flatbush that have recently sold and are slated for development, to determine the price per buildable sq ft. Basically I get an average of about $80/buildable sq ft. A developer might spend $100-300/sq ft to build, and then, if recent condo sales are a guide, the building is worth about $500-600 sq ft as either a rental or condos. He gets the difference in profit. The bigger the building, the generally lower price per build able sq ft.
I'm assuming that developers themselves have made these types of lists in order to determine a fair price for a building project.
Using this metric, one can also determine whether or not a building has a good chance of selling. being torn down, or being rehabilitated in some other way. For instance, 150 Lenox, currently for sale for $2.75m for 15,000 build able sq ft, is almost $190/buildable sq ft. It's overpriced. But perhaps a developer could add stories on top and bring his construction costs down. Or offer the seller less. According to even the highest priced sale here, it should be well under $2m. At a certain point it looks better to keep the building as is, or even to sell to an owner/occupier, perhaps at around $1.5m, about the prices of similar 3 story limestone buildings on Clarkson.
buildable sq ft price price per sq ft
780 new york ave 6730 480000 71.3224368499257
146 linden 12696 1240000 97.6685570258349
136 erasmus 14000 580000 41.4285714285714
733 rogers 15045 1300000 86.4074443336657
212 linden 17083 2200000 128.783000643915
111 erasmus 18000 1150000 63.8888888888889
8 Fairview place 22138 1440000 65.0465263348089
226 linden 23360 1450000 62.0719178082192
154 lenox 28343 3550000 125.251384821649
2155 caton 32118 3490000 108.661809577184
2100 bedford 60000 4600000 76.6666666666667
88 linden 60500 4140000 68.4297520661157
310 clarkson 145456 10000000 68.7493125068749
318-350 clarkson 200048 13100000 65.4842837718948
123 linden 376,507 18500000 49.1358726398181