The only reason the Saudi’s dropped the price of oil is because ISIS is a dagger pointed straight at Mecca, and the Saudi Royal House. They have already told other OPEC members to bugger off about the price drops.
ISIS is funding themselves with oil money, and this is how the Saudi’s intend to stop them.
I believe that ISIS is a major cause of Saudi living with lower priced oil.
Saudis have reasons better than shale to let prices fall
http://www.freerepublic.com/focus/f-news/3225105/posts
With oil, the Saudi regime always takes the long view. With security, however, its motivations are more immediate.