If the global price of materials means that it isn't possible to build a housing unit for less than $40,000 then in places where $40,000 isn't an affordable housing cost, your only options are to somehow lower global commodity prices or somehow raise local wages. Both of which are hard, and neither of which are particularly specific to the housing market. It's just not a place where that problem can be solved.
Whereas if the global price of materials means that it is possible to build a housing unit for $40,000, but local regulations make it cost $800,000, and then as a result local housing costs are $800,000, that is a problem in the local housing market.
Whereas if the global price of materials means that it is possible to build a housing unit for $40,000, but local regulations make it cost $800,000, and then as a result local housing costs are $800,000, that is a problem in the local housing market.