Serious question: What was Apple's official reason for mostly-limiting user inside access to their machines for RAM and SSD upgrade purposes? Was it really only about greed?
Serious answer - yes, there are genuine technical advantages to using soldered-in RAM and, at least, not using bog standard M.2 SSD modules - none of which explain Apple's upgrade prices or base specs.
RAM:
MacBook Pros- like many "ultrabook"-style PC laptops - switched from regular DDR RAM modules to LPDDR (low power) RAM years ago to improve performance vs. power consumption. LPDDR chips
have to be surface-mount soldered to the logic board, as close as possible to the CPU, as the length and impedance of the tracks leading to the CPU are a factor in power consumption vs. speed - until
very recently, plug-in LPDDR RAM modules didn't exist. That's why many thin & crispy PC laptops have non-upgradeable RAM too - ones with upgradeable DDR4/5 RAM will take a power consumption vs. performance hit. With Apple Silicon, Apple went for LPDDR RAM across the board, and went to the extra step of mounting the chips directly on the processor package, making the tracks even shorter and probably squeezing out an extra drop of performance. M-series chips do offer comparatively high RAM bandwidth. (Soldered-in RAM started with the 2012 Retina MBP, which used an interrim tech called DDR3L - I don't know if that
had to be soldered but it probably ruled out cheap bog-standard DDR3 sticks).
In the last year, Samsung have announced a standard for plugin LPDDR modules - I'm not sure its been seen in the wild yet and I wouldn't hold my breath waiting for it, but the idea of a M5 package with LPDDR6 'wings' is a nice mental image...
SSD:
There's no excuse for this to be
soldered in - seeing as the Studio and Mac Pro
do use plug in flash modules which could be upgraded if Apple deigned to allow you (...maybe they're taking a power consumption hit?) However, regular M.2 NVMe or SATA SSD modules include a controller (basically: a computer that makes a bunch of flash chips behave like a virtual disc and talks SATA or NVMe protocol to the host). Recent Macs have had a SSD controller built in to the CPU (...and, before that, in the T2 chip on later Intel Macs) that talk more-or-less directly to the flash chips on the logic board. That also has all sorts of advantages in terms of speed and security/encryption. but rules out the use of cheap M.2 drives as primary storage - even the Pro and Studio modules are proprietary. If they added a secondary M.2 slot they'd have to find some spare PCIe lanes to drive it.
Of course, you could get a Mac Pro (which seems to use disc controller in the second die of the Ultra chip to provide PCIe lanes) and stuff the slots with NVMe drives...
