If they’re DDR4 (or even DDR3), it has no value to e.g. OpenAI so it shouldn’t really matter

But it's a cascading effect, OpenAI gobbled up all of DDR5 production to the point that consumers are choosing to upgrade their older DDR4 systems instead of paying even more to upgrade to a new system that uses DDR5. As a result, DDR4 ram is at a new all time high - https://pcpartpicker.com/trends/price/memory/

DDR4 prices are up 2-6x in the last couple months depending on frequency. High end, high speed modules (e.g. 128GB 3200MHz LRDIMM) are super expensive.

Isn’t that due to different reasons (like the end of production for older standards)? I recall the same happening shortly after manufacturing for DDR3 ceased, before eventually demand essentially went to 0

Even RDIMM / LRDIMM prices have recently started going up. And I thought that those would be safe, because neither "big AI" nor regular consumers need them.

Demand spills over to substitutes.

The price of DDR4 is also going up!