I see your point. But do they just give you money or other things too?
And if I sell them, will my other save games be able to find them on other planets? Like if I decide my other space planet should collect 10 rare stones or whatnot, if I 'sold' one of them in my other save game, can it still be found for the other save game? As in, are they fixed on planets or are they all duplicated and scattered across the Universe?