For instance, this deal from early in the Tim Cook era:
>Apple today announced that it has reached long-term supply agreements with Hynix, Intel, Micron, Samsung Electronics and Toshiba to secure the supply of NAND flash memory through 2010. As part of these agreements, Apple intends to prepay a total of $1.25 billion for flash memory components during the next three months.
https://www.apple.com/newsroom/2005/11/21Apple-Announces-Lon...
If you go back to the time when Apple was looking at single sourcing their SOC production at TSMC you'll find some interesting comments in the press.
>The world's leading foundry chip maker Taiwan Semiconductor Manufacturing Co. Ltd. is considering operating single-customer wafer fabs, according to chairman and CEO Morris Chang.
Chang, speaking to analysts on a conference call to discuss the company's second quarter financial results, said that the market is tending to produce fewer higher volume customers and some are so large they need their own dedicated fabs.
https://web.archive.org/web/20120728040723/https://www.eetim...