Price per square foot is attractive because it compresses a complicated asset into one number. In luxury residential real estate, that compression can obscure the features that create the largest spreads in value. Two apartments in the same building can trade very differently because one clears a neighboring roofline, has a better bedroom wing, higher ceiling heights, superior light, a terrace, a fireplace or a more compelling renovation.nnThe more singular the property, the less useful a broad neighborhood average becomes. Good valuation work triangulates recent trades, competitive active inventory, failed listings, line-specific history, renovation cost, replacement difficulty and the current depth of qualified demand.nnPPSF belongs in the model. It should not be mistaken for the model.