Remember, margin decisions are made for the product line, not a single product alone. Apple doesn’t say “let’s set the margin on the base model and see what we can squeeze from the suckers”, they say “based on decades of sales data we expect a particular mix of sales, and need this margin to justify the product line, so we recommend this pricing model to achieve those aims”.
I agree that they don't make decisions for a single product, not even for a single product line, but for entire device categories over several generations, as much R&D, logistics infrastructure and other such long-term costs are shared. And when determining things like general build quality, available specs and prices for those specs they also take into consideration the expected costs of warranty claims, expected service life of the product and replacement rate by customers. I never claimed that Apple's management decisions are irrational, if anything perhaps they err on being a little too rational. You could claim, and you'd probably be correct, that the light bulb manufacturers I mentioned earlier had no option but to cartelize to offer lower-quality bulbs because the business would cease to be sustainable if people were able to purchase bulbs that last forever for a dime. From their perspective competition on quality was a race to the bottom, and could very well put most of them out of business. Most markets are not simple and perfectly competitive, but complex structures where many sorts of perverse incentives are at play, and the more complex a product is, also the more this is true, more on this below.
What I think the buyers of higher end machines are getting by paying more is a machine more capable of satisfying their higher end needs.
Remember: pricing is set at the level a customer is willing to pay and the company is willing to accept. A customer is willing to pay a price at which they value the product more than the money. At the higher priced end of the lineup customers either value the product more (eg. they can earn more from their business by using it, have a hobby they particularly enjoy, or find status in the item) or the money less (eg. they're wealthy enough they automatically buy up market because it saves them effort evaluating different products or it makes them feel good to spend it). At the lower priced end, they either value the product less (eg. all I need is something to browse the web, write a term paper on, or access my companies online accounting tools) or the money more (eg. they'd like the fancier one but also need to replace their refrigerator this year and can't afford both).
I think Apple is quite aware of the reputational damage that would come from selling people products that don't live as long as those customers expect and the fact there are other companies out there ready to take those customers if Apple disappoints them. If you take out the assumption that everyone but us is a fool, then your theory gets pretty weak.
I don't think that computer buyers, or "everyone but us", are fools. Your assumption, which I think is wrong, is that the PC is highly competitive and that buyers yield significant power in it. They don't. Unlike the horde of fanbois we see here on MacRumors or on social media, most people buy a PC because they need it, not because they particularly fancy it. It's also for them a fairly big-ticket expense incurred only ever so often, which means that changing platforms does not come without a cost, and, depending on personal circumstances, may not be possible at all. In the case of Apple, force-bundling OS and hardware further strengthens their quasi-monopolistic position. And even when jumping ship is an option, the only other realistic alternative
for the average consumer is Windows, where, admittedly, there is more competition on hardware, but meaningfully only if you're savvy enough to build your own machine and in a position to forgo a manufacturer's direct support, which most people aren't. So yes, companies like Apple will take customers for a ride, not so much as to take them to the breaking point, they have to offer devices that are fit for purpose after all, but enough to be noticeable if you pay attention, as in the case we're discussing right now, where what makes financial sense for Apple feels like an arbitrary and irrational pricing structure for customers.
