This is mostly only true in cities where lot prices are super high - which actually isn't the case in the majority of US cities.
It's hard to imagine commodities being substantially cheaper if we didn't have 30-year mortgages.
Home builder margins aren't impressive.
The cost of a new home is pretty much the cost of the lot, plus the cost to build it, plus a 10-20% margin.
That margin isn't going down a lot, even if you don't have 30-year mortgages. All that's happening is that the size of US homes would be much, much smaller.
And you might have some pressure for smaller lot sizes in places like SoCal and NorCal and Seattle.