Apple doesn't buy any of the cheap, older, low-end components. There is relatively no muscle to flex in that area. Apple flexes their muscle because they sell more computers at the high end than anyone else. It is these components that they compete for and win on.
Market share is completely meaningless when just total number of units are taken into account across non-comparable ranges. For example, the iphone and all android phones together have a minuscule market share of the worldwide cell phone market. The lion's share of that market is $20 disposable phones.
And Apple does use it's lock on the consumer devices market to muscle production in the PC sector. For example, consumer devices use a lot of flash memory. So do computers. Apple owns the world's flash memory supply right now. Last year, there was a panic in the market because Apple locked up all the flash memory, which drove the prices paid for it by other companies sky high.
Apples products are what make it special. The entire music player, pad computing and smartphone markets hardly existed before Apple created them. They did not create those markets out of thin air, marketing and mystique.
And if they did, why aren't others beating them to the punches and getting that business? Why is Apple always the one in front now? Give me examples of whole unique markets, or even unique individual products, being created by anyone except Apple.
Microsoft's tabletop computer doesn't count...
Mark