It's hard to believe it is just about pricing.
The common phrase to think of is that "it's nothing personal, but simply business." But when we hear that Samsung will not be providing memory chips and displays in the initial production volumes of the iPhone 5, we cannot ignore the fact that Apple and Samsung were involved in a bitter and rather damaging legal dispute. This one may be more personal than it is portrayed.
According to Bloomberg, industry sources "familiar with the matter" said that Samsung will still be manufacturing the processor, but the company will be dropped from the bill of materials otherwise as Apple is leveraging its influence to source components from other suppliers. Pricing seems to be the general reason, while other point to the legal battle between the two and we know that lawsuits have never been a good way to increase the loyalty in business relationships.
Bloomberg said that Apple is getting its displays from LG, Sharp and Japan Display. AU Optronics may join the supplier base for a smaller iPad.