I agree with most of your points, however, I would argue that Apple probably spends more on production costs per computer than other computer makers. Apple probably uses higher quality components on average than say Dell
A 1:1 comparison requires that they be at the same grade. If you're using a grade AA panel and your competitor has order grade A, you can't draw any conclusions from it. The conceit of the simplified example is identical hardware at identical costs, because that's the only way you can compare margins.
The example at the end of my first post is perhaps complex and underexplained (in an attempt to simplify), so although it paints the general picture, it doesn't quite add up. Here's a very simple example that should more clearly illustrate the bottom line of the complexities involved:
Dell widget. Costs $75/unit, overhead of $15/unit. $100 sales price. Net profits: $10/unit (10%).
Apple. Costs $70/unit (in-house savings), overhead of $10/unit (efficiency savings). $110 sales price (modest price premium). Net profits: $30/unit (27%).
That's how Apple pulls in piles of cash. But note you have to control for costs or you can't do any sort of math, so your point, while worth noting generally, doesn't affect the outcome here.
Definitely one noticeable difference is that every one of their computers except for the cheapest MacBook uses an aluminum body which will certainly be more expensive.
There are many such touches throughout the line, but you are comparing computers with unlike supply-side costs, which you simply cannot do. Forgive the car analogy, but it's like comparing margins of an Audi and a Chevy while pretending they have equivalent materials and engineering costs.
Apple's cost savings for equivalent hardware are a result of eliminating the middleman. One of the biggest savings for them is not having to pay Microsoft (with a Windows license running 5-10% of the overall price, highly regressive on the low end, and with a large part of that price profit for Microsoft, the fact that Apple doesn't have to pay a markup to itself is a huge savings by itself, to say nothing of in-house hardware engineering and cutting out the middlemen there in many parts of that process).
Apple outsources manufacturing, but does most of its own engineering and all of its design. People talk about the big items--chipsets, CPUs, GPUs, RAM, drives, displays--coming from the same places, but forget that most of the work and cost for a computer vendor is in everything else. Where Dell's power adapters, frame and casing, trackpads, keyboards, mainboards, batteries and lots of ICs are off the shelf or reference designs, Apple does all the legwork itself and sources the actual manufacturing only. Dell has a lot of places where they're paying a supplier's margins as part of their costs). A lot of Apple's "supplier margins" go back to themselves. If you were to add in reasonable third-party margins, Apple's overall percentages would start to look a lot more like HP's.
Apple's mainboards, lots of ICs, trackpads, keyboards, batteries, power adapters, cooling systems are their own engineering and design. Most competitors have a supplier design, engineer, and produce those pieces to specified parameters, which comes with a markup Apple doesn't have to pay.