What would Australia do if Iran attacked their embassy? They would kick them out, denying Iran an embassy in Australia. When it comes to this stuff, a tit for tat strategy is generally the common tactic. If you attack peaceful trade ships, then your own trade ships is valid target for retaliation. If you start to threaten ships with ransoms, other nations will do the same.
Invading Iran is a complete different subject compared to boarding trading ships well outside the border of Iran. Historically, a Letter of marque was a very cheap way to manage countries which did not respect your own ships. Some laws are still in the law books regarding how to deal with prize ships, which illustrate how close we are to the time where peaceful traversal of waters was not a given.
One of the biggest trade partner for Iran is China. Will China pay the toll? Will Iran attack their ships? Will China retaliate if they do? If China do not need to pay the toll, which other countries would then be willing to one-sided pay for access to the strait?
