Reminds me of a 2d space rpg I played. This was an absolutely brilliant game for me as a kid, as you could build your own space bases. And then run blueprints, colonies etc. All the EVE stuff in a MMO game but pre-Eve. (it launched a year after EVE but EVE didn't launch with things like player owned starbases right away).
So at one point I was in the top 5 players in the game and had a absolute ton of gear and actual liquidity and set up a trade hub. I never expected it but that thing took off, I was making a billion a day and you could sell a billion credits for about $10. Remember that this was a pretty obscure tiny game that was generating hundreds of dollars a month for a 16 year old, and that you could completely set up the trade hub on your base as you liked, and so I didn't actually have to put in any work. (setting up the initial shop was a pain). The beauty was that after a short time, 90% of my trade wasn't my own gear that I was finding and selling. Mostly I was providing instant, immediate liquidity to anyone. (the alternative was to spam in trade chat you wanted to sell something, then haggle, fly across the universe to meet the guy and then do a 'drop trade' based on trust without any form of escrow). My base offered a safe, secure, immediate price. And that value allowed me to discount prices and charge premiums. I was getting ridiculous 30% profit margins on other people's intermittent trading just by being a source of liquidity (in a game where there's no opportunity cost of money, there's no security to buy or interest rate to get. So there were no cons to locking up my money in trades) and gear.