Across the country, far-sighted political leaders are destroying public housing projects. From the Pruitt-Igoe projects in 1972 in St. Louis, to the Robert Taylor Homes in Chicago in 1998, to the New Brunswick Homes destroyed in New Jersey in August 2001, to the Christopher Columbus Homes in Newark in 1996 (pictured above), the failed vision of government-run housing projects is being demolished in a puff of concrete dust. Everywhere, that is, but here in New York City, where instead of getting the city out of the housing business, Mayor Bloomberg wants to build more units.

That is not to say that there aren’t some good points to the housing plans the mayor outlined this week. Mr. Bloomberg is wise to focus on removing barriers to private construction, and he is wise to include on his housing advisory panel such figures as Frank Ricci, who represents property owners fighting for a free market in housing, and Michael Schill, a professor at NYU who has written about the costs of the city’s regulatory structure. The mayor is also smart to pursue adopting the Model Building Code as a replacement to the city’s own byzantine code.

But this mayor, while happy to spend political capital on such crusades as banning smoking in the offices of Philip Morris, all of a sudden gets conflict averse when it comes to the real money sinks in the city. That’s part of the reason the mayor and other politicians claim that the city’s $6 billion budget gap can’t be bridged by cuts alone. They are ready to impose more tax increases on what is already a high-tax city.

Yet while Mr. Bloomberg claims there’s no fat left to cut in the city budget, he’s chosen not to take on — indeed, to expand — one of the oddest welfare programs in place: the fact that a select few families live for decades at public expense in public housing projects that take up some of the city’s choicest real estate.

A prominent New York real estate appraiser who we spoke to estimated for us the value of several public housing properties in the borough of Manhattan. These properties are not on the far edges of the city — they are on East 28th Street, Park Avenue, Fifth Avenue, near Central Park West, and in other revenue-generating parts of the city. By the appraiser’s estimate, selling just a handful of these public complexes would net $500 million right away, with a further $10 million a year that would be generated by adding these expensive properties to the tax rolls. Our appraiser said it would be no trouble at all to find willing buyers to manage the properties.

As our columnist J.P. Avlon has written, similar opportunities exist in Lower Manhattan, where prime riverfront real estate north of the Brooklyn Bridge is now occupied by public housing. Mr. Avlon estimates that the land that is now occupied by about 83 public housing buildings with only 9,908 units could be built to encompass about 200 buildings and 30,000 units. The sale of the land alone could generate billions in revenue for the city.

We’re well aware of the distinctions between housing built by private non-profits and that operated by the New York City Housing Authority, and of the authority’s own quasi-independent nature. We’re aware that some of this housing is paid for with federal money, and that homeless families must be put up by the city at great expense in temporary shelters, even in hotel rooms.

But we’re also aware that there are lots of hardworking taxpayers in Queens, Staten Island, Brooklyn, and the Bronx who pay their own rent and don’t understand why they should subsidize with their tax dollars a Park Avenue apartment for families who, in some cases, aren’t even poor. Temporary help is one thing. But the average family stays in city housing for 17.7 years. Though NYCHA is required to register any change in income or family size among its 425,000 residents, it does not kick out families once they pass the income threshold (about $47,000 for a family of four). A spokesman for NYCHA said that while the original intent of city housing was to help struggling families “get on their feet,” once they are on their feet “traditionally nothing has been done” to get them out of public housing.

This is how public housing has developed — a leg up became a lifetime entitlement, which now exempts prime real estate from the tax rolls and locks it in well below its potential value. Opponents of housing reform complain that people will go homeless. But when welfare reform was enacted, opponents cried the same thing. In fact, as we have seen, it has halved welfare rolls and moved more people than expected into economic self-sufficiency. Why should the same standard not be applied to housing? There is no right to live almost 20 years in a taxpayer-subsidized Manhattan apartment. Selling off some of the city’s housing projects in Manhattan and imposing a five-year time limit on the residency of most able-bodied public housing occupants would save the city billions of dollars on a one-shot basis and add hundreds of millions more to the tax rolls on an ongoing basis going forward. Call it $2 billion toward closing the gap.