> They are adding capacity as quickly as they can [...], just like everyone else
Are you sure? In the past they explicitly said they are not going to increase production.https://www.tomshardware.com/pc-components/dram/memory-maker...
Even if we ignore the fact that you can't build out factories in secret, this would be securities fraud by publicly listed companies.
> ...as margins are too high
This is not the first RAM boom-bust cycle, and memory makers are an actual cartel convicted of coordinating in the past - none if them are going to break rank when they can invest the minimum and reap outsized benefits. Also, no one wants to invest in additional capacity when the bottom can fall out at anytime, and shareholders demand your head- not even the AI companies want to bear that risk, which is saying something.