I suspect we would disagree on whether any savings are substantial, and as such whether they could justify the obvious and severe reduction in ability to upgrade or repair these devices.
Personally, I don't buy the idea that a customer goes into a store and measures whether an iPad or a Galaxy Tab is a few tenths of a millimetre thicker before making their purchasing decision. On the other hand, I do buy the idea that a lot of people are shocked and then angry after their Apple gear gets damaged and they learn how much it's going to cost to repair and how long it's going to take, not least because I personally know several people who have been stung in that way. Of course, by the time they discovered that downside to the all-in-one designs, Apple already had their money.
The idea that it can only make a difference if people measure it is absurd. People buy Apple products because they look nice and work well. Shaving space and weight is part of their design. I know people buy iPads instead of Galaxy Tabs because of the industrial design. I seriously do not believe that the iPad could have such a nice design if it was fully modular. I'm sure you can come up with a bunch of individual components to modularize without substantially impacting the design, but that doesn't do us any good. Unless I misunderstand your complaint, they'd have to modularize many components, and that will definitely impact the design.
In my experience, people are mostly surprised as Apple's good service when they need a repair. It's not like other manufacturers provide cheap repairs, either.
Personally, I don't buy the idea that a customer goes into a store and measures whether an iPad or a Galaxy Tab is a few tenths of a millimetre thicker before making their purchasing decision. On the other hand, I do buy the idea that a lot of people are shocked and then angry after their Apple gear gets damaged and they learn how much it's going to cost to repair and how long it's going to take, not least because I personally know several people who have been stung in that way. Of course, by the time they discovered that downside to the all-in-one designs, Apple already had their money.