If you are just going to use in-game information, rare goods trade is going to be very limited.
There is some mention in the game:
- I think the engineers state where the rare goods they require are from.
- You can very occasionally find rare goods dropped by NPCs - I've seen a total of 4 of these in 3 years.
- Rare goods CGs usually state where to get their goods can be bought.
- There was once a CG for all rare goods. All the legal ones were listed in the commodity market, but only the rare good's names gave any clue where to get them.
- I've heard rumours about NPCs that offer missions to fetch rare goods. Never seen one, and have no idea where to find these.
- A few NPC crew mention rare goods in their backstories.
I remember the Sothis Gold CG, and the engineers ones have the system in their name I think - I have unlocked all the engineers (not the new Colonia ones).
I think there is a general tendency for the Devs to assume communication between players which puts me at something of a competitive disadvantage, but I generally don't compete with others.
There is a great deal to find in this game, most of which I have not discovered in-game - the Guardian stuff is a good example. I know it exists, a station I frequent sells the Guardian gear but I have no idea where to start looking for the sites (in-game). A quick google would easily tell me but I don't want to find out that way, I want to 'discover' it in-game.
I appreciate my style of play is not for everyone & certainly no one should be forced down the path I choose to take, but sometimes I think it would be nice if the Dungeon Masters considered my style of play when they add these puzzles into the game. And of course Rares are just another of those discoverable easter eggs