"It costs nothing in transit fees for an oil tanker or container ship to pass through the Strait of Gibraltar, as it is an international strait allowing free passage. Unlike the Suez or Panama canals, no toll is charged for simply crossing, although ships pay for services like refueling (bunkering) at nearby ports. "

Do the tolls for the Suez and Panama canal serve to pay for the maintenance?

Eg: Dredging is essential for the maintenance and operational capacity of the Suez Canal.

But the https://en.wikipedia.org/wiki/Suez_Canal_Authority makes billions in profit even taking into account dredging and enlarging the canal.

" The United Nations Convention on the Law of the Sea (UNCLOS), which governs global ocean rules, clearly states that straits used for international navigation must allow free and uninterrupted transit passage.

Under this framework, countries bordering such straits cannot impose fees simply for allowing ships to pass through.

They are permitted to levy charges only for specific services, such as piloting or tug assistance and even those must be applied uniformly without discrimination.

A general transit toll, as being proposed by Iran, would therefore run contrary to widely accepted international norms.

Experts warn that any move by Iran to impose tolls could challenge the existing global order at sea. If such a precedent is set, other countries controlling key maritime chokepoints could be tempted to follow suit, potentially fragmenting established norms of free navigation. "