Exactly. Iran has nothing to lose economically by going after Saudi oil. Before the sanctions against Iran, the status quo was OPEC as a vehicle to divide up the dollars. Everybody in the region profited from that arrangement.

Now that the sanctions are in place that former arrangement no longer keeps the peace. Iran wants in on the action and if they can't have it, they'll go after the Saudi's. They've been putting their ability to do so on display with not so subtle actions.

The US has two options here: 1) go to war with Iran. 2) find a way through diplomatic channels to make this go away. It looks like Bolton (aka. option #1) is out and Rouhani is meeting with Trump to discuss option #2.