http://www.reuters.com/article/us-mideast-crisis-usa-syria-idUSKCN0XL0ZE
I'll give you an idea on the cost:
"The the average strike cost during the past few months of operations in Syria and northern Iraq against the Islamic State is
$2.5 million. This comes from the Center for Strategic and Budgetary Assessments report “Estimating the Cost of Operations Against ISIL.” Here's what it includes (these are all averages):
Intelligence, surveillance, and reconnaissance, 75 percent of which is provided by UAVs
Most strikes are carried out by F-15s, F-16s, and F/A-18s, with the AV-8Bs, B-1s, and F-22s doing a little here and there. The strikers will carry three weapons and drop two.
Gas for strikers, ISR birds, and tankers
If the number of strikes increase very much, another carrier is going to be needed, which will up the cost by about $200,000 per strike"
http://www.slate.com/blogs/quora/2015/09/06/u_s_bombing_isis_in_syria_how_much_does_one_airstrike_cost.html