Intel and AMD __literally__ sell those broken chips to the open marketplace, recouping at least some of the costs (or possibly getting a profit from them).

Apple probably does the same strategy PS3 did: create a 1-PPE + 8-SPE chip, but sell it as a 1-PPE + 7-SPE chip (assume one breaks). This increases yields, and it means that all 7-SPE + 8-SPE chips can be sold.

6-SPE-chips (and below) are thrown away, which is a small minority. Especially as the process matures and reliability of manufacturing increases over time.