Not getting much bang for your buck
US spending on Islamic State fight totals $2.7bn - BBC News
$9 million a day, in my simple maths that's a billion a year and so far you think you have killed 10,000 terrorsts without really gaining any territory. So that's $100,000 a terrorist, at that rate you could pay them to leave the battlefield and have the same effect. A cost benefit analysis would suggest this scenario isn't very effective and the cost is about to increase. I have a distinct feeling of dejavu and I see a Gulf of Tonkin comng on, that incident that will see a scaling up isn't far away