I agree with your general sentiment, but please let's not be naive about Apple's business practices - last time I checked (2 years ago?) Apple's company wide profit margin was about 30 - 40%. So yes, Apple's products are superior and you definitely get something in return for the higher price, but the Apple Tax itself is definitely real.
While that's true, I've also read years and years of stories about how virtually every PC maker other than Apple is dancing on a razor's edge due to paper-thin margins. Dozens of manufacturers in the last two decades have gone under, been bought out or left the market; PC laptops used to be (and may still be, in some cases) crapped up with bloatware and festooned with stickers because each sticker you have to peel off and each bit of software you don't want is necessary extra revenue; the survivors like HP and Dell seem to bring in more profit through enterprise-level service contracts than hardware. And in the smartphone business, there have been quarters where Apple and Samsung together are making more than 100% of the profits because everyone else lost money.
...so, it at least seems plausible to me that Apple may be setting the prices for their PCs and "post-PC" products more correctly than most of their competitors. Even if that's true, the Apple Tax could still be a thing -- but the premium may be magnified by the "lose money on every unit and make it up in volume" tactic so many PC makers seem to have had through the 2000s.
True but only to a point. Apple's scale gives them a price advantage from suppliers, which increases their relative margins.
Also note that not all parts that seem comparable are. For some parts like LCD panels that have more variance in quality, Apple has deals with suppliers to get the best panels while Dell and others have to buy the ones that don't hit quite as stringent QC.
Both of these are why looking at margins alone doesn't give you a complete picture.
