I will now brand myself a heretic.
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Wait for it....
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Fasanomics works just fine (at least in this particular case).
The bottleneck seems to be in transport tons available, either thru dropship or jumpship scarcity. Tonnage however, is only part of the transport equation. Caloric/nutritional density is the other, more important variable, and as luck would have it, is still officially undefined (outside of space travel).
"Bulk" foodstuffs are not going to be ears, or even kernels, of corn; they're going to be high fructose corn syrup which has three times the caloric density of just the kernels. And that's to produce a substance that can be used immediately. I'm pretty sure the caloric density could be increased by a factor of ten or more, if the engineers designing the process were allowed to stipulate that reversing the process so the calories could be consumed would require substantial reprocessing.
Add in the passage of a thousand years and a bright, glorious Star League, and there's plenty of room at the bottom. Highly compressed blocks of pure protein, all cellular components removed, artificially stabilized for long term storage, could provide the needed minimum nutrient for ten's of thousands of people, per ton. It might take a month to process it back into something approaching edible, but the number of DS/JS visits you need to keep a population fed quickly plummets to more manageable levels.
Either define the caloric density of bulk goods, or, even simpler, add: "Only the use of heavily processed high density bulk foodstuffs make trade, and colonization, on such a scale (barely) possible." Do that and none of the previously published numbers need change, just our assumptions about undefined aspects of the 'verse. Assumptions, I would point out, about a science fiction universe.
Edit: Spelling