What do you think the cost of oil will rise to if Iran stops exporting? Of course if they stop exporting oil the will have no income.
The entire Persian gulf region produces 27% of the worlds oil at this time.

"In 2003, Persian Gulf countries had estimated net oil exports of 17.2 million bbl/d of oil (see pie chart). Saudi Arabia exported the most oil of any Persian Gulf country in 2003, with an estimated 8.40 million bbl/d (49% of the total). Also, Iran had estimated net exports of about 2.6 million bbl/d (15%), followed by the United Arab Emirates (2.4 million bbl/d -- 14%), Kuwait (2.0 million bbl/d -- 12%), Iraq (0.9 million bbl/d -- 9%), Qatar (0.9 million bbl/d -- 5%), and Bahrain (0.01 million bbl/d -- 0.1%). "
Link
http://www.eia.doe.gov/emeu/cabs/pgulf.html