The two best-known analyses of the war’s costs agree on this figure, but they diverge from there. Linda Bilmes, at the Kennedy School of Government at Harvard, and Joseph Stiglitz, a Nobel laureate and former Clinton administration adviser, put a total price tag of more than $2 trillion on the war. They include a number of indirect costs, like the economic stimulus that the war funds would have provided if they had been spent in this country.

Mr. Wallsten, who worked with Katrina Kosec, another economist, argues for a figure closer to $1 trillion in today’s dollars. My own estimate falls on the conservative side, largely because it focuses on the actual money that Americans would have been able to spend in the absence of a war. I didn’t even attempt to put a monetary value on the more than 3,000 American deaths in the war.

Besides the direct military spending, I’m including the gas tax that the war has effectively imposed on American families (to the benefit of oil-producing countries like Iran, Russia and Saudi Arabia). At the start of 2003, a barrel of oil was selling for $30. Since then, the average price has been about $50. Attributing even $5 of this difference to the conflict adds another $150 billion to the war’s price tag, Ms. Bilmes and Mr. Stiglitz say.

The war has also guaranteed some big future expenses. Replacing the hardware used in Iraq and otherwise getting the United States military back into its prewar fighting shape could cost $100 billion. And if this war’s veterans receive disability payments and medical care at the same rate as veterans of the first gulf war, their health costs will add up to $250 billion. If the disability rate matches Vietnam’s, the number climbs higher. Either way, Ms. Bilmes says, “It’s like a miniature Medicare.”

In economic terms, you can think of these medical costs as the difference between how productive the soldiers would have been as, say, computer programmers or firefighters and how productive they will be as wounded veterans. In human terms, you can think of soldiers like Jason Poole, a young corporal profiled in The New York Times last year. Before the war, he had planned to be a teacher. After being hit by a roadside bomb in 2004, he spent hundreds of hours learning to walk and talk again, and he now splits his time between a community college and a hospital in Northern California.

Whatever number you use for the war’s total cost, it will tower over costs that normally seem prohibitive. Right now, including everything, the war is costing about $200 billion a year.

Treating heart disease and diabetes, by contrast, would probably cost about $50 billion a year. The remaining 9/11 Commission recommendations — held up in Congress partly because of their cost — might cost somewhat less. Universal preschool would be $35 billion. In Afghanistan, $10 billion could make a real difference. At the National Cancer Institute, annual budget is about $6 billion.