So what does [Marc] think a spaceport on a world with a population of twenty billion would look like?
When I asked him specifically about Mora, he seemed to lump it in with the "Big and Bustling" category, which would mean on the order of tens of thousands of passengers (he batted around numbers like 10,000 and 25,000) arriving and leaving per week. 1,000 ships arriving per week, 1,000 ships leaving per week, and appx 5,000 ships berthed at any given moment.
For your example of a 20-billion-person world, it's literally one in a million people who travel in space per week.
Of course using CT you can't boil it down any further than those generalities. On the other hand, for the purposes of playing the game, you need go no further in that direction.
I'm starting another thread to muse on this.