I agree if Apple wanted to build laptops to score better than "1" on iFixIt, they probably could do it, though there would be costs in terms of weight, thickness, cost of components, supportability, etc.
Why are those "costs" automatic? Do you know that for sure or are you just speculating such "costs" to make it seem like the way they chose to go is the one and only way to get something pretty close to the end result?
For example, they didn't have to choose "proprietary pentalobe screws" for these products, though that does contribute to the iFixit score of "1". Choosing a non-proprietary screw would have NO effect on their ability to deliver this exact same product (no thickening or weight gains).
The shapes of the batteries appear to fit into battery-shaped slots. Everything seems thoroughly packed in. Why do they need the battery glue? If the shape of the batteries fit the slots and there is no room for them to move around in there, why glue them down? Conceptually, the lack of glue doesn't change thickness, weight, etc unless it's very, very slightly more favorable.
Does the ram and flash memory have to be soldered down to achieve the same thickness, weight, etc? No way to slot it? This one is probably arguable but I would guess that Apple could make it work without soldering if they wanted to do so... without having to fatten the case or make it heavier.
I can't talk to "cost of components" very well. I would assume that there would be a little more cost in slotted ram & flash vs. soldered. Only Apple can talk to "supportability." But both cost of components and supportability seemed to work fine for Apple when they made laptops without soldering those parts down. Again, it didn't seem to be a huge problem back then. Besides, I'm yet to see anyone question whether Apple can easily make their margins on this rMB. Personally, I suspect pricing is such that there is a good deal of room in there for some additional unit cost (but of course, I can't know that for sure).
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For Apple, the whole top cover gets replaced as the battery is glued to it. So the price is actually for a battery and a palm rest which may also include the trackpad.
...by design though. It doesn't have to be that way. That's they way they chose to make it. I suppose the automakers could make it such that car tires required replacement of the entire wheel (not just the tire but the wheel parts themselves). Maybe they could engineer the wheel so that one pretty much must replace the brakes if they replace a wheel? And maybe engineer the brakes so that one must replace the struts when they replace the brakes?
So then we rationalize a manufacturer repair bill that exceeds what it could be by saying "the whole wheel, brake and strut gets replaced when you blow a tire". See how that works? Take our love for Apple out of the scenario and it's much less appealing. Why is the battery glued to the top cover? Why does replacing a battery possibly require replacing a perfectly fine trackpad? Other than Apple deciding to glue down what appears to be a fitted battery, why do we pay for a new palm rest and maybe a trackpad too? (rhetorical, but hopefully illustrating the point).