The square foot cost to build a house would be based on the total cost of the scope of work divided by the total square feet of the finished product.
The average costs for a structure is relevant to the structure that will be built to the extent that the question would be the same as to ask "how much does it cost to buy a car by the pound?"
The word is spelled square.
As the Jibs'ls are flown FORWARD, the "SQAR" you refer to must be a SPAR, known as the bowsprit.