Or supply/demand was bugged. It makes no sense that hundreds of commanders endlessly fly T9s filled with crap back and forth to pretty much irrelevant stations and earn obscene fortunes in no time while doing so. Its a bug in the BGS, not a sensible feature. The BGS should result in temporary 'gold rushes' that you find yourself for you and some friends. If endless number of people can endlessly grind it for no discernible reason it has nothing to do with supply/demand in the first place.
In other words: trade missions need to be tied to the commodity markets.
It only makes sense if demand increases again without the hand of god, once the hauling stops.
If you make the entire galaxy homogeneous from a trade standpoint, it's not worth the time it takes to engage in it.
Example: How do they get materials out to Colonia? If you haul something there, you'll get bubble prices for it. Surely there's not a contingency of commanders marathon hauling every commodity back and forth from Colonia to the bubble. So that indicates that there's no supply/demand in play.
I agree with temporary gold rushes, that should mean that you can move around and find them. You won't. You'll find bugs that result in a simulation of a gold rush, and the balancing of the market happens via hand of god after someone on reddit or youtube makes it publicly known and it gets spammed to death.
Maybe it's a bug but it's indistinguishable from just a poor BGS and too much tweaking.