Without nitpicking the unified building code to smithereens I would like to point out that labor costs on construction (excluding systems work like plumbing and electrical) typically run roughly 3x materials costs. Insulation requirements get pointed to for the switch to 2x6 or bigger studs but the ugly truth of the matter is lumber quality has declined to the point that larger boards are needed to make structural load requirements. Likewise a huge chunk of the increased cost of building comes from the sheer volume of products that have to be applied to keep OSB and engineered timber from reverting to it's native state (a pile of sawdust), which is again an issue being driven by inferior materials.