I think the one factor is purely volume. Apple has a very small range of laptops, compared with other manufacturers. And they have a relatively large market sha

I think the one factor is purely volume. Apple has a very small range of laptops, compared with other manufacturers. And they have a relatively large market share for the segment of the market they compete in ($1000 plus laptops). Hence, for x dollars of sales, they sell 1 model - compared with their competitors, who all have to sell many more models. So they can spend significantly more on the R&D and design for each model, and still be profitable. This shows in their systems.