Obviously nobody knows the yields of the PS3/XBox processors and the exact prices negotiated between the companies (except the parties involved and IBM certainly is not going to tell us). However, rough estimates on yields are known and even if there were uncertainties in the 10-20% range, that would yield to roughly the same differences in chip prices, which again would result in price differences in the single $ digits. None of the other points you bring up have _anything at all_ to do with estimating the manufacturing costs. It really is important to have insight into mass manufacturing processes (and how expensive things are on that level - and I have come across many surprises within the past 25 years when I tried to estimate stuff without knowing the facts behind them) when trying to figure out the manufacturing of a mass market gadget (something you obviously lack so don't make up invalid points to argue).
Yields are a closely guarded secret. So really inferring Xbox CPU/GPU yields from information on other processes, which is at best a good estimate isn't going to give you an accurate picture. So really, if you want to back up your earlier statement tell me your estimated cost for both the Xenon and the Xenos Cpu given your estimated yields and the die size can be found on http://www.anandtech.com/gadgets/showdoc.aspx?i=3152&p=3 as well as pictures of the internal components.
So what I really want to know is this. How much does it cost for each Wafer, how many chips/working chips can be produced on every wafer and the packaging and testing costs which should yield the price per chip. To help you out the GPU is produced on TSMCs 80nm process and the CPU is produced on TSMCs 65nm process.