for computers compared to brands such as HP, Dell, or even Acer, how can they have more buying power for their computer builds than these other giants?

I will grant that Apple does have the lock on portable music devices and tablets, but they are no where close to the volume of the PC companies. Therefore they cannot command volume buying power on such things as hard drives, or video cards or even Intel processors or memory chips.

Now this is in fact a '09 chart, but Apple's share of traditional desk top or laptop computers still has not gone over 15% in the total market... They OWN the music and tablet business with the ipod and ipad. But they are losing market share with the iphone as Droid type devices gain ground.

Apple marketing and mystique is what makes Apple special.