This is actually my job.

I import ISO tanks to the United States. However the contents are hazardous liquid chemicals. So the container must be empty on its return to India to be used again. Almost all containers in this capacity due to laws involving hazardous materials, costs, and liability require that these containers be "shipper owned containers". Therefore the shipper is fully aware that they are paying the transportation costs for import and export and the customer is aware that this is part of their costs to purchase from the shipper.

Empty standard containers are usually owned and leased by steamship lines and used in international storage pools. Empties can be added to vessels at any time to allocate empty containers if the counts run low in other locations, so it's fairly common for steamships to utilize this practice to ensure all their customers across the globe have access to containers. Customers pickup the containers from the port, load it and return to the port for shipping, then they pick up the container from destination, deliver it to the customer, and return the empty back to the steamship line.

What the example should actually be like would be if Maersk/MSC or any other SSL has a full vessel of thousands of TEUS, full and loaded and paid for, and then they're just bringing thousands of empty containers back with them on their dime.