Yearly costs in Iraq have nearly doubled since 2003, from $48 billion to $94 billion. According to the Mercury News, if this keeps up, the war will cost $660 billion by 2016. This is apparently based on the Whtie House's anticipated request for $50 billion next year.
It seems to me that that is an extremely conservative estimate; if current trends continue, I see no reason why the White House would only ask next year for a little more than half what it asked for this year. So it seems to me that the true number is likely well over a trillion by 2016, unless we start drawing down significantly in Iraq.
That is all.