It's definitely relevant to the overall housing market, because while 20 years ago the bankers and lawyers would have rented or purchased on the Upper East Side or Upper West Side, they're now (often) priced out and buying places in Brooklyn and the Bronx. 15 years ago I used to see a working class neighborhoods when I walked around on the far side of the river in Brooklyn, LIC or even Hoboken/Jersey City; now there are multi-million-dollar apartments there.
Any time you hear investment bankers talking about how they can't afford a 2-bedroom in Manhattan, something's gone seriously out of whack with the real estate market.