Groceries are an excellent example of competition. Profit margins on groceries are razor thin. The large chain leverage results in lower consumer prices. Large grocery chains don't have anomalously high profits, ROI, or really anything that would indicate harm to consumers. Groceries are cheaper than ever compared to median wages.

The memory market is international, its not clear what anti trust even means here. Even so, look at the price of memory over time, say the last 20-30 years. Adjust for inflation and its even more extreme. Sure, it is up recently with AI demand, but the general trend is drastically reducing cost and increasing quality. Memory technologies are evolving quickly and it's a capital-intensive business, so its not surprising that there are a few leaders. There's no guarantee of instant competition in free markets.

Cartels rarely last long without enforcement. There's such a strong incentive to defect and secretly sell more under the table. Even OPEC could not maintain one. Memory right now is expensive simply because demand outstrips supply and there is significant capital investment and lead time to increasing supply.