The US war on ISIS in Syria, when it hasn’t centered on the offensive near Kobani, has mostly been a war on oil. Airstrikes have pounded oil wells and refineries across ISIS territory, which is also the primary oil-producing part of Syria.
It’s being couched as an effort to cut off ISIS funding, but the oil wells and other infrastructure being targeted are actually privately owned, and the attacks are badly damaging the civilian economy across Syria.
As winter nears prices are soaring, and not just on fuel. Knock-on effects have raised the price of almost everything, including basic food. The prices of grain are no doubt also effected by US airstrikes on grain silos in the north.
Even though the oil-rich east has been lost by the Syrian government to ISIS, much of the oil still finds its way back into Damascus through smuggling. ISIS was doubtless getting a cut from some of that smuggling, but it’s not the only one paying a dear price from the US attacks, and with a lot of its finances coming from taxation and extortion, ISIS is probably much less effected by the US air war than the ordinary Syrian.