Unfortunately, no. Brownstone type buildings and townhomes not only vary in size, they are in different neighborhoods which makes them vary in price also. It would be extremely unfair to put this type of house on a scale due to these two factors, which would be slightly misleading to the public.
There was an article put out by "The Real Deal" that might be of interest:
If you are in the market for a brownstone, I have sold quite a few of them throughout the years and know the various neighborhoods throughout Brooklyn. I grew up here... It is my home.
give me a call anytime: 212.300.3919
Happy Hunting Scott!
Keller Williams Realty Empire
9120 4th Avenue Brooklyn, NY 11209
M: (212) 300-3919
O: (718) 954 8400
F: (347) 587-2828