Here's the USMC bragging about burning two barrels per gun and 35,000 rounds of 155mm ammo to kill ISIS fighters "by the dozens"
http://www.businessinsider.com/m777-how ... -combat-13
"In five months they fired 35,000 artillery rounds on ISIS targets, killing ISIS fighters by the dozens," Troxell said.
Those 155mm howitzer rounds have to cost as much, if not more than, tank main gun rounds. Let's say $30,000 each (M982 rounds are $70,000 each https://en.wikipedia.org/wiki/M982_Excalibur). That's over $1 billion of our taxpayer dollars just for ammo.
Back in my bad old days, a US Army artillery battery was about 150 men. An artillery battalion was about 3 or 4 gun batteries and a HHC. My CAV troop, almost 200 men, burned about $50,000 in payroll and about $15,000 in food every week. Again, that was 30 years ago, so multiply by 4. We also burned about $100,000 in fuel for every week in the field, but I figure artillery doesn't move as much as we did. That comes out to about $25 million to keep a battalion in the field for 5 months (men are cheap). Let's figure about 5x that number of support troops (supply, medical, transportation, etc.) to keep those guys in the field for 5 months (I'm being generous - the US Army was about 10 ash-and-trash troops for every trigger puller), so another $125 million.
Total cost: about $1.2 billion USD
Let's say "dozens" means 5 dozens of ISIS fighters - if it was more than that, he would have said "hundreds". That's 60 ISIS fighters killed.
That comes out to $20 million USD for every ISIS fighter killed.