The Congressional Budget Office estimates the “cash for clunkers” legislation that passed the House this week could generate sales of 625,000 new vehicles. There are more optimistic estimates of a million sales.

Really? With national unemployment at 9.4%? Until that goes down, and with it the level of workplace insecurity, I suspect most folks will be more concerned with keeping the “clunker” running, especially if it’s paid for.

I get the legislation. Ideally, it’s a “twofer”: getting older, less efficient and more polluting vehicles off the road and stimulating sales, in which we, as now part owners of GM and Chrysler, should all have an interest. The legislation is backed, not surprisingly, by not only the Detroit automakers, but also by the UAW, the National Automobile Dealers Association, the U.S. Chamber of Commerce and other business groups.

But there’s no free lunch. The price tag on the House-passed bill is pegged at $4 billion — and that’s on top of the billions already propping up Detroit’s bankrupt pair and a number of industry suppliers. Plus, the legislation doesn’t specify that your new vehicle has to come from a U.S. company or even an American factory.