>Those are unreliable and vary at the whim of the government and their need to fill a hole in the budget.

Sure, but that doesn't matter to the guy buying the trailer. They got a tax break, credit, whatever, and through the magic of financialization they sold that tax break for $.92 on the dollar. So they don't really care what happens. And the $.08 hedges the middle man's risk. Etc. etc.