Who else are they going to buy displays from? There are only approximately five companies that have the capacity to manufacture displays at such a large scale: LG, Samsung, Toshiba, Sony, Hitachi - and they supply practically every company such as Apple, Dell, Viewsonic, etc.
Short of Apple opening their own plants and manufacturing their own display I don't see who else Apple can buy displays from. They make approximately 175 million iDevices per year on top of the 15 to 16 million macs per year.
Do you know any other company that can supply close to 200 million display panels per year to one company, let alone other companies that need displays?
I'm not trying to downplay everyone's display issues as they are legitimate issues which Apple has to deal with but there's only a handful of companies that can supply Apple.