Okay, then yeah; I've seen that happening. Or some other weird thing; my Cahoona Meatsteak complexes are getting money somehow, but I don't allow NPC traders, I have no UTs running, and they've got a jump range of 0, so either they are selling to my own ships, or they are selling to NPCs.
That said, I would kill for an "empire trade" option. "If you need resource X, go buy it from any of my stations within jump range." That kind of thing would be fully transferable in presets (like the Local option, which I'm really enjoying) since it's not location specific. It would also simplify inter-sector logistics in a big way; instead of setting up new orders at my existing sectors to feed resources to a new sector every time, I can just add more resource production/consumption and let the trade AI move those goods around as needed. As long as production is high enough within the region defined by jump range, I could add sectors or different kinds of production and have it integrate seamlessly into my logistics network.
As it stands, I have to try to forecast future consumption and set up supply chains accordingly. It ends up being a feast or famine kind of thing if I get it wrong, with my DAs burying one sanctuary in resources while others end up with shortages. I could try to rectify this by creating spillover DA jobs where every sanctuary has a threshold beyond which they will try to supply every other sanctuary, but this results in exponential growth in DA jobs and is a ton of work anyway. It would be a lot easier to let the trading AI handle this so the player can focus on higher level economic planning instead of micromanaging every route.