That's today. You have to think about what the industry is going to look like in a decade.
Building a DRAM company from scratch is hard, expensive, and risky. You're burning a fortune to get started, and the result is a commodity product. But the AI bubble allows CXMT to have terrible yields, sell a legacy product, and still make a healthy profit! This is literally a once-in-a-lifetime opportunity to catch up.
And yes, right now that means selling DRAM for 10% below the crazy AI-inflated prices the incumbents charge. But sooner or later either demand will drop or supply will catch up. CXMT, like many other Chinese companies, is undoubtedly willing to operate at razor-thin margins to increase market share. Either the other manufacturers move down as well, or they'll be made irrelevant by CXMT stealing all their customers.