Janina~when you are comparing apples to apples in a specific location, the living sq ft space does give you a good comparable to determina a selling price.
However, you have heard the old saying: Location-Location-Location!!
I have a SKI HOUSE for sale in the most valued and coveted area of Salt Lake City near Snowbird + Alta Ski Resorts. The living area of my listing per sq foot is much higher than a home not in the Little Cottonwood Area.