Oils value at the global strategic level is not how much you get for selling it, but how important it is to keep it flowing in the global economy. Saudi resource nationalism was tamed by enticements, Iraqs by invasion. Iran however seems to be rather stiff necked about the whole affair.
While nationalized after 1972 the Iraqis continued to sell oil on the open market and ship it. The Saudis supply restrictions were not about saving the oil for themselves but rather about getting a better price and Iran is open to foreign companies, it has been for sometime. The contracts are service agreements but that has not stopped companies like Total and Statoil from participating. The only restriction on Iran has been external through the Iran Libya Sanctions Act imposed by the US and further more recent sanctions imposed by various countries with regards to the uranium enrichment program. Iran would be shipping and selling all they can if they weren't subject to sanctions.