My first system built pays 400k credits/week (specifically, 410,042 Cr with a Score of 41.00), and I spent a lot less time hauling building materials than I would for 40 different outposts that each give 10k credits/week.
40 outposts is roughly 800k tons of materials needed for construction. A single Coriolis, an additional outpost, and the various buildings needed to build a profitable system is roughly 150k tons, maybe 200k if you really build things out. The real money comes from setting up an efficient system with a decent population and high stats (especially Wealth).