Condo or home? Carriage house or full house? Big house or small house? As mentioned above, all will effect price per sq foot. When determining a good buy, price per sq foot is seldom used as the sole factor. It works better when comparing identical condos, but not in diverse construction and location like you have in Rosemary Beach.
The average price per sq foot for the two homes sold in January 2011, in Rosemary Beach, sold at an average price per sq foot of $895. In all of 2010, the homes sold in Rosemary averaged $417/sq ft on the selling price.
Again, don't rely solely on price per sq foot to determine whether or not this is a good deal. By the way, the prices/sq foot I'm quoting are for heated/cooled sq footage only. Not for courtyard, and unconditioned space. I'm not sure why you are using the figure of half the unconditioned space as it would be a PITA to track prices.