> extortion
not really; you would have to pay to run an oil pipeline through another country's territory even if that country wasn't bearing the cost of maintaining the oil pipeline
the strait isn't international waters -- it's part of Iran and Oman's territorial waters
For land pipelines thiere no eqauvalent of the United Nations Convention on the Law of the Sea according to which both Oman and Iran should allow free passage of ships. And "normal" path lies on Oman's waters which dones't stop Iran from attacking ships there. The strait toll is a pure racketeering.