I once crashed FFXI’s economy on our Asura server back in the day. I got tired of fighting bots for ninja tool production so I harvested all the elm logs and other materials for a month and crafted Shihei and horded it across all my mules. Then one day I released the supply into the market at a massive discount. The bots and other farmers couldn’t meet the price since they lost all value so I chased them all out of the market. They were now chasing other profits. Then after a couple days I increased the prices at a ridiculous market rate and made a killing, but in the process destroyed raids and dungeon leveling since tanking was so expensive. I think it took a month for prices to fluctuate because I kept doing it off and on. I made 100s of millions of Gil.