I understand that a full compliment of containers is around 800kg just in the containers.
There's a fair bit to the container loading system, adds around a tonne to the aircraft EW.
The containers themselves are nowhere near 800kg for a full fit. The 'generic' weight of an AKH container is 80kg but in reality, some are canvas, some are Aluminium so when they're weighed they're usually less than half that amount.