Nearly $1bn already spent on US military campaign against ISIS — RT USA
If the airstrikes moderately intensify and 5,000 ground forces are
deployed, the cost would be driven to $350 and $570 million per month.

A
pair of U.S. Air Force F-15E Strike Eagles fly over northern Iraq after
conducting airstrikes in Syria, in this U.S. Air Force handout photo
taken early in the morning of September 23, 2014. (Reuters/U.S. Air
Force/Senior Airman Matthew)