Money, and lives ("blood and treasure").
Also note the 23 US WIA and the ANA/etc. WIA, of which 5-10 are going to be permanently disabled, and all of which together probably cost more in medical treatment than the munitions expended. Plus of course all of the time spent training those people to do an inherently negative-sum task.
This is why the decision to go to war should not be taken lightly, and why it is important that if you do go to war, you fight it to win as quickly as possible.