I think Apple should have separate lists: bestelling iPods and accessories, and bestselling Computer/Hardware/Software.
Remember that there are now two divisions at Apple: iPod and everything else. I am curious to see how this will play out in the next, oh five years or so.
Comparing computers to software, iPods, and accesories is like comparing tacos to icebergs - it doesn't work. That is why I it doesn't bother me too much that a Mac isn't in Apple's list, though it would be nice for it too be in it. It does make me happy that Macs hold 10 of the top 20 spots on Amazon...
Also notice that the average price of all the items in the top 20 is around $100. It only makes sense that they would sell a higher volume of these things. I mean it's much easier to impusively buy a case for your iPod shuffle than to buy a 3 grand laptop.