I'm not reading anything about bad yields from that Bloomberg article. Just about scarce parts but that could be attributed to any number of reasons.
From the Bloomberg article: "The company’s biggest headache is ensuring a reliable supply of DRAM and NAND flash memory, with both in high demand as smartphone makers gear up for fifth-generation devices, according to people familiar with Sony’s operations."
Your claim on what Bloomberg said.
"If, as rumours suggest, Sony's chip yields are shit and they need to come in with a higher price than Xbox"
So why are you not making a reference to the actual origins of the rumor?
Edit: Found the source.
Sort of a variable target though. If you are looking for the cream of the crop chip and not getting as many, you're bound to have poorer yields than a lower binned chip. Sony wouldn't be aiming for cream of the crop, this would be crazy expensive because you're literally binning everything...
forum.beyond3d.com
Now I know why you didn't want to use the actual source.