Costs to construct a home on 30a are typical of any other coastal Florida market.
Calculate the cost of all materials to build a building and you have the cost. The difference in SoWal is what the human element believes they deserve.
Ask any experienced builder to calculate the cost of all the materials on your job first excluding all labor. If they can't give you the cost of all the materials combined then move on to someone else who can.
The cost of "materials only" to build a house in Rosemary Beach is somewhere near $75 per square foot. WaterSound Beach $73, Watercolor $71, Alys Beach $70. Then calculate the labor for every trade. A yard of 3,000 PSI, regular rock, no fiber concrete is currently +- $94. A 3,000 sq ft Alys Beach 100% concrete home will use approximately 320 yards of concrete