There is also no evidence to back up the implication that Apple's primary reason was to prevent third party upgrades. Based on what I've heard from people who

There is also no evidence to back up the implication that Apple's primary reason was to prevent third party upgrades. Based on what I've heard from people who work (or worked) at Apple, that isn't normally how they roll - usually there's a cost, performance, user experience, security, reliability, or functionality (etc.) reason and breaking third party upgrades, compatibility, or repairs is just a happy (for Apple) side-effect. ;-) Placing the SSD cache in unified RAM would seem like a plausible performance and cost justification to me, not "wild speculation" as you claim. I've seen papers describing how to optimize the use of flash storage that require low-level control of the device as well as modifications to the OS/file system or even the cache and memory system - all things Apple could certainly do. However, as you note, evidence will tell. Regarding whether Apple passes its own savings on to customers, I will note that the Disk II was said to be "obscenely profitable." In general Apple maintains some of the highest margins in the industry. Which is not to say Apple products are a poor value (I generally consider them an excellent value for what you get, and for my own use cases) but it is saying that they are very good at keeping money in their own pocket.