Am I underestimating the wealth of TL1 Anarchies, or of TL15 CorpStates, or are Oolite planets a lot more economically homogeneous than modern-day nations (maybe throwing in some handwaving about how a lot of wealth is concentrated in the hands of the rich), or is something else entirely going on?
Ultimately I think the problem is that these numbers - cooked up for what was expected to be a throwaway game in 1984 - were never intended to bear any real scrutiny …
True, but reverse-engineering ridiculous throwaway numbers into something that makes sense is at least as much fun as just handwaving it all. (Next up: Coming up with a set of ideas to choose from, explaining in-game planet sizes versus populations of billions.
However, there's also the fact that GDP (or, in this case, GPP) is a horribly inexact method of calculating economic output. What might account for the apparent smallness of the difference between the simple pastoral (?maybe nomadic/hunter-gatherer) rodents of Maesin and the ultra-sophisticated high-tech avians of Ceesxe could be the vastly higher level of efficiency on the latter world. For example: communications on Maesin could be dependent on a network of runners, signal fires, and messenger bats, whereas citizens of Ceesxe enjoy direct wireless neural connection an ultrafast system-wide net. Although the infrastructure costs are obviously hugely greater on Ceesxe, the per-mile cost of sending a message is much, much higher on Maesin. So on Maesin, a lot more work has to be done to achieve a fraction of what can be done on Ceesxe.
Does that make sense?
It's at least /an/ explanation, which is one more than I had to work with an hour ago.
I'm wondering whether the Maesinites would necessarily be quite so pre-technological as you describe, though. Is there any more info about low Tech Levels than TL2 covers Oolite-quality missiles and rerouting systems for larger cargo bays? Depending on what counts as a "good enough" missile, then TL1 could cover anything up to roughly World War 2 level tech, or up to better-than-present-day tech.
Also, there's further complications between natively-produced tech, and what tech is available via import; for example, a lot of present-day third-world nations are leapfrogging some issues with infrastructure by jumping straight to mobile phone networks instead of trying to lay landlines everywhere. Even if the Maesinians are as migratory as you make out, they might mirror mindsets more like Modern Mongolia than Middle-Ages Morocco.
(... Also, I'm currently thinking of various social arrangements that would allow people who average an income of 1 Credit per year to collect 65,000 of them; if they scrimp and save and increase risk of not having enough to feed themselves, by each contributing 10% of their annual income to the cause, and take 10 years to gather the wealth, that's still 65,000 individuals making significant impacts to their lives to gather the resources for even 1 stock Adder. Which puts a certain rather significant amount of social pressure on the shoulders of the pilot of said Adder to make that investment worthwhile...)