Where there's demand for goods, people will pay for those goods. More demand, prices go up. You're right tho, competition will bring prices down. And there will be those who would rather not pay for mats and will gather their own mats. But for those who find mats gathering to be a chore us players who have mats to spare will part with those mats, but at a premium price, because we know there are those out there who hate gathering mats so much that they would pay a lot not to have do the things they hate.
Going further with this, us mats merchants may form a monopoly, keeping prices artificially high so that we become obscenely wealthy, and we may end up buying planets, maybe entire systems......![]()
Higher prices > More people willing to supply > supply drives down prices. You're overestimating how much your fellow players are willing to feed into a zero sum game, especially those living the dream where their regular activities result in surpluses (also you've got to consider low effort mat sources). If you think you can for a monopoly through so many players, more power to you. You'll have accomplished something I've never seen in any decently populated player economy.
In which case I'd say you'd probably clean up in economics IRL. You sure you don't want to apply that motivation to real life profits?