I bet it's almost all this [1]. it was like $100+ a barrel back in 2014. It's a tough time to be in the oil business.

http://www.cnbc.com/2016/01/19/oil-prices-fall-further-on-gl...

So, ISIS earns 1/5th the daily revenue of than Clash of Clans, or about the same revenue as ~250 McDonalds stores?

http://www.gamesindustry.biz/articles/2014-02-11-clash-of-cl...

As a sanity check: ISIS soldiers earn between $400 and $1,200 a month, plus a $50 stipend for their wives and $25 for each child, according to the Congressional Research Service.

Call it ~1,000 / month or ~30$ a day. Let's assume 1/3 of that 1 million / day goes to fighters and the rest is overhead. ~= 10,000 fighters which is a significant force and importantly it's replaceable with new recruits.

PS: Though that could significantly understate things if the average is closer to say 500$ per month and / or overhead is lower and paid with other income sources.

Those numbers seem far too high. ISIS pays soldiers more than China and Russia do?

This may be a question of direct vs. indirect pay. China and Russia both provide food / shelter / equipment which ISIS may skimp on. Also, ISIS is in a major war relative to there size so hazard pay is an issue.

Anyway poking around the web it looks like they are somewhere between 7,000 and 35,000 fighters which seems to be in the right ballpark for 1Million / day revenue.

PS: And of course graft is a major issue.

Small note, 1/5th of the daily revenue for Supercell as a whole, not for Clash of Clans alone (although that is likely the lion's share).

This doesn't change the overall thrust of your point. Just noting for accuracy only.