Each region is different with cost. The project was in PA and we used a lot of NY trades and the savings, to use SIPs in place of conventional framing to achieve the same R-value, was noticable.

Note, one would have to use 2x10 studs with batt insulation to match the same R-value with a 6" SIPs. Spray foam could be an option, but the client has told us that it's the tightest house he has ever lived in and he heats it with a small stove.

Check this Houzz question that talked about a flash and batt system. It's an intermediate step between convention framing and full spray foaming.

https://www.houzz.com/discussions/flash-and-batt-insulationyes-no-maybe-dsvw-vd~771315