And those semi’s do not have to lift any of their load off the ground. Also, an airship does not have lifting surfaces (wings) to provide lift. All lift in an airship comes down to the amount of mass that a volume of lifting gas can lift; the more cu-ft of gas, more lift.
Absolutely true, but again irrelevant to my point. There are one heck of a lot cheaper ways of slowly getting something from one place to another than using an airship.