I read somewhere that the cost to get the stuff out of the ground is only $5 - $10 a barrel. That’s why ISIS can afford to charge only $30 a barrel. The rest is profit. But some countries have grown dependent on the profit for their existence.
Russia doesn’t produce much beyond oil/gas and weapons.
For whatever reason they have major budget issues if oil goes much below $100 a barrel.
What did ISIS pay for? The stole the production they are selling.
A few well placed bombs would keep that oil from ever getting to market and deprive them of millions a day, even at fire-sale prices.
There's enough slack in the market now to do it without anyone being any worse off than they were a couple of months ago, too.