While it is monumentally expensive to build a fab, this is very much an overstatement for a number of reasons:
* The "expensive" part is mostly the R&D and large scale tuning/yield of a whole new process node. But this doesn't apply.
* The timescale involved is likewise for a whole new node and/or building in a new territory. Also doesn't apply.
* They would be well on their way to completion by now if they started back in 2024.
* Even DDR4 would be relieve some demand.