So they are getting four times as many processors for the same size wafer as they were at the beginning. So a Cell now costs 25% of what it did originally. All other things being equal.

The site you quote actually says :-

“Moore’s Law, states that the number of transistors on a chip will double about every two years.”

That doesn’t mean a halving of price, it means a potential doubling of power, far from being the same thing.

Sony won’t gain this advantage because the cell processor hasn’t doubled in transistors in the last two years, its stayed exactly the same. They may have had some cost reductions by increasing the yield per wafer but this won’t be anything like a 50% price drop.

Most of the cost reduction will be as you say from redesign and sorting out Blu-Ray production, not from chip price reductions.