Thus the average you seek will not provide a very useful answer.
Falmouth MA has over 70 miles of coastline, and other towns have none.
Building costs are more a function of the location's restrictions and requirements than ever before.
I would contact a local real estate professional in the town(s) you are focused on to help with this answer and to save time and money.
(I'm on the Cape, but I can help you choose a local pro if you want help doing so.)
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I suggest taking a trip to a 'box' store and browse the prices of materials, including kitchen and bath complete packages. The large price variations for a single component e.g. roof, the bargain shingles vs. lifetime warranty high end shingle can double the cost. Kitchen cabinets - use per linear foot can be triple depending on the craftsmanship.
Another good measurement of costs is modular home construction. I have visited several modular home companies and also their assembly plant. The pricing is fairly straightforward and can be a great source for price comparisons. You will be able to see the cost of upgrades for kitchen, bath, flooring, windows, electrical fixtures, doors and windows is not dissimilar to 'options' or 'trim packages' on a car. The quality of materials will stand out. Labor for installation will remain the constant low end to high end.
In the end, the more you know the better consumer you will become.
California and the Southwest has large home construction companies. They achieve savings in volume of new builds, but the individual general contractor may offer cost reductions with modifications to the house plans.
Take your time and be aware, you will be pleased.
Also the site work itself could be costly (town water? town sewer? or well and septic? ledge? Basement or slab?
Windows Harvey, Pella, Andersen? Levels within each manufacturer.
How many bath?
Are you doing it yourself or hiring a contractor to over see it?
A rough figure above land would be 175 a foot. It may be able to be done for less, but most people will go over.
ps Ron, I am also a licensed builder.
There are builders on here but most of the good ones are VERY BUSY in MA right now!
Try reaching out to:
Patrick Perkins CR,CLC
28A West Main St Millbury Ma 01527
508-865-4063 fax 508-865-9553
Old World Construction
Any of those three contacts can give you some great information regarding building costs.