> but chip lithography errors (thus, yields) at the huge memory density might be partially driving up the cost for huge memory.
Apple's not having TSMC fab a massive die full of memory. They're buying a bunch of small dies of commodity memory and putting them in a package with a pair of large compute dies. How many of those small commodity memory dies they use has nothing to do with yield.
This has been pretty clear about all Apple chip designs, going back to some of the first A series afaik. They are "unified memory" but not "memory on die", they've always been "memory on package"-- ie. the ram is packaged together with the CPU, often under a single heat spreader, but they are separate components.
Apple's own product shots have shown this. Here's a bunch of links that clearly show the memory as separate. Lots of these modules you can make out the serial or model numbers and look up the manufacturer of them from directly :)
Apple's not having TSMC fab a massive die full of memory. They're buying a bunch of small dies of commodity memory and putting them in a package with a pair of large compute dies. How many of those small commodity memory dies they use has nothing to do with yield.