…On average, says appraiser Jonathan Miller of Miller Samuel, “the price difference between a second and first floor apartment is 15 percent. The difference between a second-floor apartment and a third-floor apartment is probably another 10 percent”–meaning that the difference in price between a first and third floor apartment can be as much as 25 percent.

The reason? Market perceptions about security, privacy and street noise. “The exception, of course, would be a brownstone garden apartment,” says Miller, which will sell at a premium. The first floor in a walk-up is also a premium — think an inverse relationship of price to stairs….