No, a wafer is very much not a wafer. DRAM processes are very different from making logic*. You don't just make memory in your fab today and logic tomorrow. But even when you stay in your lane, the industry operates on very long cycles and needs scale to function at any reasonable price at all. You don't just dust off your backyard fab to make the odd bit of memory whenever it is convenient.

Nobody is going to do anything if they can't be sure that they'll be able to run the fab they built for a long time and sell most of what they make. Conversely fabs don't tend to idle a lot. Sometimes they're only built if their capacity is essentially sold already. Given how massive the AI bubble is looking right now, I personally wouldn't expect anyone to make a gamble building a new fab.

* Someone explained this at length on here a while ago, but I can't seem to find their comment. Should've favorited it.

> Sometimes they're only built if their capacity is essentially sold already.

"Hyperscalers" already have multi-year contracts going. If the demand really was there, they could make it happen. Now it seems more like they're taking capacity from what would've been sold on the spot or quarterly markets. They already made their money.

Sure, yes the cost of producing a wafer is fixed. Opex didn’t change that much.

Following your reasoning, which is common in manufacturing, the capex needed is already allocated. So, where does the 2x price hike come from if not supply/demand?

The cost to produce did not go up 100%, or even 20%

Actually, DRAM fabs do get scaled down, very similar to the Middle East scaling down oil production.

DRAM/flash fab investment probably did get scaled down due to the formerly low prices, but once you do have a fab it makes sense to have it produce flat out. Then that chunk of potential production gets allocated into DRAM vs. HBM, various sorts of flash storage etc. But there's just no way around the fact that capacity is always going to be bottlenecked somehow, and a lot less likely to expand when margins are expected to be lower.

> So, where does the 2x price hike come from if not supply/demand?

It absolutely is supply/demand. Well, mostly demand, since supply is essentially fixed over shorter time spans. My point is that "cost per square mm [of wafer]" is too much of a simplification, given that it depends mostly on the specific production line and also ignores a lot of the stuff going on down the line. You can use to look at one fab making one specific product in isolation, but it's completely useless to compare between them or when looking at the entire industry.

It's a bit like saying the cost of cars is per gram of metal used. Sure, you can come up with some number, but what is it really useful for?