The network effects of Apple devices are really tiny, compared to say: Microsoft, which holds nearly every company in Europe ransom in effect because Excel is a default tool you need to interact with your government in nearly every country as a business.
Sure, your iPhone doesn't connect as seamlessly to your Windows computer as it would a Mac, but those aren't network effects, thats vertical integration.
Nobody is forcing you to buy a Mac, and Apple themselves are intentionally overcharging for upgrades on the basis that: "If you really need it, you'll pay for it". Most people don't need it but will buy the upgrades anyway then complain that they're too expensive.
I'm aware that it limits the longevity of the devices, but that might also be intentional here, not abusive though. Just a bit bare-faced profit seeking. Which seems to be working because, as you point out, it's one of the worlds most valuable mega-corporations.
If someone else comes out with good premium laptops I'll move over happily, but for now the best laptop you can buy is unfortunately a macbook, and they've decided that upgrades are worth this money, if you don't agree then the answer is to simply not upgrade, or avoid the devices entirely.