I'm not sure that anyone can truly answer that question. The builders do not typically put that information in the mls so the agents don't always have it available to us. There is also a huge difference between high end and low end builders, the amenities that are being included in the home, the density of the homes being built (ie single family, villas, condos, apartments, etc), whether you are including the land, or just the building. Are you building a frame building or brick? Basement or slab? How many garage spaces? What is the lay of the land? Is it flat and level and easy to build on or very rocky, hilly and needs a lot of extra's to build. Is it a subsidized project or not?
I can look at a small 3 bed 2 bath home in North county that a builder built using subsidized funds from the city and county on land that was essentially given to him by the city in order to have it developed rather than have it sit as vacant land vs a huge 6 bed 8 bath "castle" in West County on several acres with lovely views and an 8 car garage, rosewood floors and it's own wine celler and bowling alley.
Your best bet is to go back to the builder in question and ask the builder what his average cost per sq foot was during that time period for a home like the one that you are interested in, however, prices then have nothing to do with prices now