Apple absolutely loves to gouge for upgrades, but the chips in this have got to be expensive. I almost wonder if the absolute base model of this machine has much noticeably lower margins than a normal Apple product because that. But they expect/know that most everyone who buys one is going to spec it up.
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.
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 :)
- Side-by-side teardown of M1 Pro vs M2 Pro laptop motherboards showing separate ram chips with discussion on how apple is moving to different type of ram configurations: https://www.ifixit.com/News/71442/tearing-down-the-14-macboo...
- M2 teardown with the chip + ram highlighted: https://www.macrumors.com/2022/07/18/macbook-air-m2-chip-tea...
- Photo of the A12 with separate ram chips on a single "package": https://en.wikipedia.org/wiki/Apple_A12X
- M1 Ultra with heat spreader removed, clearly showing 3rd party ram chips onpackage: https://iphone-mania.jp/news-487859/
price premium probably, but chip lithography errors (thus, yields) at the huge memory density might be partially driving up the cost for huge memory.