Costs “per/sf” are like the 10-day weather forecast: they exist because there is a huge demand for them and the fact that they are usually woefully inaccurate is hardly ever factored. To use a favorite Bushism, there’s a lot of misunderestimating going on.
When comparing costs per square foot it is critical to make sure you are using an apples-to-apples comparison. On the top of the equation ask yourself what costs are included. Does it include landscape, hardscape, permit fees, architect and engineering fees, cost of money, sales tax and contingency?
On the bottom of the equation, what exactly, is the area measured? Just livable spaces, or are the garage, mechanical, storage, covered areas, deck and patio areas also included? Manipulate these numbers for any project and you can easily have a 100% swing.
And that’s not accounting for the human factor; sometimes the most telling metric would be the delta nose length, measured before and after some people spout out these numbers.