Your math is impeccable except I would multiple that one year estimate by the number of years the clunkers would still be on the road. Cash for clunkers was about spending money not saving anything. It was an auto industry bailout, scored points with their green wing, a direct bribe of 700,000 consumers with a government gift, a brazen display of YES WE CAN marxist flavored intervention. All in all on the scale of usual federal waste it was a winner. Using any other flavor of mathematics and economics it doesn't make sense.