I suppose that goes without saying. If it were cheap and easy to build, there wouldn't be high demand.
Would it really be that cheap, though? Hell, even a single wide trailer built in a factory, which is about as ideal as it gets from a cost perspective, is still a home largely out of reach of the average Joe.
It remains unclear who is going to buy all these new houses unless they are sold at a loss — but who is going to build a home with a plan to sell it at a loss? You?