Remember when Bilmes and Stiglitz published The Three Trillion Dollar War: The True Cost of the Iraq Conflict  in early 2008? There was much discussion about how it wasn’t true, how they’d overcounted this, and undercounted that. (E.g. 1 )
Well, it turns out it was indeed not true.
It’s costing four trillion dollars . ($4,000,000,000,000. Actually, with those sorts of numbers, you’re really supposed to use scientific notation: $4 x 1012.)
That’s just the loss for the USA. It doesn’t count the cost for the troops of other nations. It doesn’t include the costs in Iraq. All told, six or seven trillion dollars’ worth of smoke and rubble is probably a cautious and conservative estimate.
The good news is there was nothing else that needed doing, so it’s not as if it matters.