The Cash for Clunkers program increased car sales. Sales went up for Ford and VW, but down for Daimler and for Chrysler.
The aggregate additional sale came at a high price in government spending. This is because cash for clunkers payments were made on some car sales that would have happened without the program. How much did it cost the government to increase total sales? About $7,200 per additional car sold (with a maximum benefit per deal of $4,500).
The first time home buyer's credit costs about $43,400 per additional buyer (with a maximum benefit per deal of $8,000). It is a real credit although there is a penalty for a quick flip of the house.