Typically an empty 20 foot shipping container weighs between 1.8-2.2 metric tonnes (about 3,970 - 4,850 lb) and an empty 40 foot shipping container weighs 3.8 - 4.2 tonne (8,340 - 9,260 lb) depending on what kind of container it is. For example, high cube containers tend to be heavier.
Yes, especially with the container shortage[1] reported earlier this week, I would be very surprised if empty containers are being sent away from where there already is a shortage.
