General Discussion

When a ship docks in port, they are charged a port due based on either the gross or net tonnage of the ship. Tonnage in this context is a measure of volume and not of weight.

Ports also charge a goods fee based on the type of good being loaded or unloaded. This may be per ton (weight in this context, not volume) if it is a bulk good or will be per twenty-foot equivalent unit (TEU) if it is containerized. If a ship (un)loads a container, it's going to contribue to their TEU whether it has anything in it or not.

There are then a bunch of other fees that are added on - pilatage fees, early/late arrival fees, crane fees, etc...

No ship is arriving in the United States and being $0 in fees.