Everything also has the same volume, which means everything has the same density. So either the 1 ton of tea is highly compressed, or the 1 ton of palladium is a small nugget in the middle of a whole lot of packing peanuts.
So I agree with the OP, more from an immersion point of view, because density should vary. For example, I should be able to carry more tonnage of diamonds than water, as neither are compressible.
yes and no. tonnage would be same but everything would not have same volume. For some things sure, could see how advanced form of compacting could allow much lower cubic meter volume needed for any given ton of that item. But for many items, no - they are either not practical to compress by much or can’t be.
so volume would definitely not be the same. In ED the devs i assume decided to focus only on Tons for simplicity, but while I am no expert on space, I can talk about maritime shipping which I believe some physicist should be able to confirm is reasonably similar for limitations on space hauling.
in maritime shipping, every nation uses the same standardized shipping container specs - there are number of different spec containers but 2 most common are 20 and 40 foot containers. A 20 foot container (aka TEU) can hold ~33 cubic meters volume and is ,ax rated for 28 tons. If your freight consigned for that container takes more space or weighs more, it doesnt go.
for simplicity, most ppl refer to container ships by # of containers it can carry - a Panamax container ship can carry 5000 TEUs, the more modern New Panamax can carry 13k TEUs, which can then be translated into total cubic meters and tonnage of freight it can carry. But regardless the total cubic meters of cargo carried, the weight (or mass in space) is the real limiting factor - based on weather season and fuel range, it can be foolhardy to carry above a certain total weight / mass. The engines can only drive so hard and i would assume in space the mass would be the main limit (aside from the physical matter of fitting the freight into whatever max volume is available). Higher weight / mass = lower speed (or thrust in space).
aside from safety factors, speed = life and death profit for container ships, a few days late penalty is massive for shipping much less the profit per idle day loss. So what we are talking about here is in ED we ought to have both a cubic volume rating AND tonnage or mass rating per ship to determine how ’much’ cargo we can carry. Every cargo item ought to have both a cubic meter value and tonnage value - and whichever limit is hit first, then no more cargo can be loaded.
just like IRL container ships, either you carry a whole lot of volume that weighs very little, or a relatively small volume but highly dense cargo that weighs a lot. (Or some combo of the two with neither limit being reached, or 1 limit of cubic volume or mass being reached first). In ED terms we either carry 500 tons of ore that fits in relatively small cubic meter space in just 1 cargo hold, or fill every cargo hold to the brim with some low mass cargo like feathers.
this still doesnt help OPs request though, b/c without much larger bulk carrier ships being available to players, he could fill a Cutter to the brim in terms of max cubic volume with food cartridges but the total tonnage would be low (and hence sell only a few tons of profit) or it would be some super special magic compressed food nutrient cartridge like gold bars but would then hit the total tonnage / mass limit far before cubic volume of cargo capacity was used up.
the only way OP could get what he wants is if ED ignored tonnage / mass completely and just used a cubic volume limit only rating - which would then allow a whole lot more food cartridges to be shipped. But hate sounding like a loop recording but this would also put us back to square one - why ship a whole bunch of small volume food cartridges when you could ship almost just as many gold bars?
the solution, if we need one, are classes of ships that can carry a much higher volume of low mass cargo, aka grain ship or bulk food carrier. Put in ED terms, a cutter that can carry 500 tons of any cargo as we do today, or the new SuperBarge that can carry 5000 units but only from this list of low mass cargo - food, feathers, blankets, etc