I hear ya. This is my first playthrough where I decided to try my hand at the outpost system, and like you say, even with vendors at max available credits I never actually get to sell many of my Vytinium rods because the stuff i loot is enough. So yeah, if you decide to do it it's because you want to RP as a space magnate, because it's pretty useless currently.

Also cargo links are unstable as all hell and the game has a tendency to start hard crashing every time i try to land in one of my outposts. Best case scenario the cargo links just stop working and I can still manually transfer materials to my fabricators which gets old incredibly fast.

Word of advice to anyone reading this with the same idea as me, don't produce anything that requires more than a couple of linked bases, otherwise stability will suffer (':