Each new revelation about the degradation of New York’s subways seems more shocking than the last. But it all comes down to one thing: New York’s leaders have failed the millions of people who use the transit system every day.

The latest dismaying detail comes from a report by Brian Rosenthal in The Times, which concludes that the Metropolitan Transportation Authority, the state agency that runs the subway system, spends far more to build tunnels and extend train lines than agencies doing comparable projects elsewhere. Its construction projects have more workers than those in other cities, and workers are kept on hand even when there is no need for them. Contractors add a premium to their bids, claiming it compensates them for dealing with the M.T.A.’s bureaucracy. And some unions and contractors negotiate wages and work rules without any say from the authority.

Billions of dollars that could have gone to maintaining and improving the subways, which use a signaling system that dates to the 1930s, have been wasted on exorbitant costs. Projects have also been delayed by mismanagement.

Blame for these costs belongs to politically powerful construction companies and labor unions that drive up costs under the lax oversight of public officials who have no incentive to rouse sleeping legislative watchdogs.