While I think Apple is a prime candidate to do something like this financially, I’ve never had the impression that they ever want to get involved in something “just” for vertical efficiency. There’s always a long-term vision where they can leverage it to gain a competitive edge that their competitors can’t match (the PA Semi acquisition being a perfect example of this).

RAM doesn’t seem like something where simply owning the manufacturing could lead to a disproportionate competitive edge. It would just be a vertical efficiency gamble that may or may not pay off. Of course that could simply be a failure of my imagination.