Since the price of crude oil is sliding down, close to 20 per cent in the past two months, the Iranian theocrazy is getting less money to spend on nuclear weapons and foreign adventures such as in Lebanon.
I do not know the average production cost, but the production cost in Iraq is $1.0-1.5 according to
http://www.mees.com/postedarticles/oped/v49n10-5OD01.htm Thus a similar estimate would be valid for Iran. This means that get at least 20 % less money.
According to this article
http://www.iranmania.com/News/ArticleView/Default.asp?NewsCode=46038 the price will probably fall further as hedge funds are deserting their previous bets on new hurricanes and the Saudis are pushing the crude oil price further down to prevent Iran to get money. New fields will as be added.
It should be added that it is in the interest of the oil producers to now and then push the price down in order to prevent big coal-to-liquid-fuel investments to be made (require about $ 35/bbl) and prevent large scale biofuel production.
However, Iran has a big potential according to this 2003 article:
http://www.mees.com/postedarticles/oped/a46n47d01.htm:
"Iran is one of the large-reserve holders among OPEC member countries but its oil production capacity is proportionally less than the size of its reserves. In contrast, the production capacity of OPEC's small-reserve holders is proportionally greater than the size of their reserves. Theoretically speaking, Iran could have much higher oil production capacity. Although this subject is more complicated than the simple proportionality comparison, nevertheless the country could and should make every effort to expand and maintain its oil production capacity commensurate with the size of its oil reserves."
The reason that Iran is not investing in their production is that they are lacking money and technology, and if there will be sanctions their economy will be hurt even more.