> Average expected teu is 30k lbs on a ship
Yeah, average. That doesn't mean that every container - or even most containers - are loaded to that weight per TEU. Indeed, it's highly likely that they're not; the heavy containers are going to be toward the bottom, and the lighter containers are going to be toward the top. And there are probably a lot more light containers than heavy ones, because...
> Nearly all containers are packed to the brim
Volumetrically, yes. Not necessarily in terms of weight. Indeed, unless you're shipping gold ingots or something, "max goods shipped" necessarily means that you're more likely to run into volumetric limits first.
Not to mention that the max container weight in practice is usually a fair bit lower than the ISO spec, since those containers have to get to their destination - which means traveling on roads and railways with their own weight limits (both for the whole vehicle and per-axle), and on vehicles that themselves are part of that limit (and themselves have limits of their own). And further, a container can only have so much weight stacked on top of it.
> Real life is not pleasant to armchair theory.
Indeed it is not, which is why when it comes to the containers themselves I'm speaking from experience as a professional in the supply chain / logistics field :)
(But yes, admittedly my knowledge on military helicopters is less substantial, so if there's someone who's not an armchair theorist on that topic who wants to chime in, that'd be most welcome)