I mean there's no reason to believe that the scale and prices of the star sector economy would be at all related to how they are on earth. It's clearly established in lore that ships are constructed with nano-forges and other technology that doesn't exist, so it's not clear at all how expensive that would be. It's also not clear how expensive raw resources are. It could be incredibly cheap to construct and operate a ship if the manufacturing technology was advanced enough and the resources were cheap enough. It might then be profitable to run small scale trade to supply something that isn't produced on a small colony.
What is reasonable for a trader to do is based on what is profitable, and what is profitable is based on made up technology, so there's no connection to how the economy of earth works.
This is a pretty decent explanation for how a small number of people can put out such a large amount of industrial capacity. It isn't really clear how much automation has advanced; but it isn't too difficult to imagine that setting up a decent mining operation may simply require someone placing a box labeled "Starter miner kit", pressing a button and have it build itself an entire mining facility on it's own without having ever been present.
I think the ships in star sector are 3D printed, or at least something similar to that. Apart from a few small cases with the bigger factions (Tri-Tachyon, Hegemony), no one appears to be designing brand new ships, instead relying on "blueprints" to be able to manufacture ships. Perhaps even the manufacturing facilities for starships (aka heavy industries/orbital works) is also built from a simple fully-automated package that requires very little user input.
In any case, I think I would actually like to see player colonies scaled down a bit; getting populations above 10^8 shouldn't really be possible in the time frame of the game, at least not without mass migration from bigger colonies like Chcomoztac which would probably not make the Hegemony all that happy.
Actually, looking at the Planet screen by size, Hegemony is much much bigger than any of the competing factions (looking at each factions two biggest planets):
Hegemony:1 x 10^8 population planet
1 x 10^7 population planet
Sindrian Diktat:2 x 10^7 population planets
Luddic Church:2 x 10^7 population planets
Persean League:2 x 10^7 population planets
Tri-Tachyon:1 x 10^6 population planet
1 x 10^5 population planet
Seems power isn't all about population as Tri-Tachyon can somehow hold their own against the Hegemony despite having a significant population disadvantage. Perhaps power is much more contingent on ownership of old Domain artifacts, than manpower.