[WallWextra]

I do believe SOI has some cost disadvantage, and this contributed to its unnpopularity. The POWER8 chips are huge and probably can't be made cheaply, or to consume sane amounts of power. IBM would have to take a very thin cut to compete with Intel.

[pinkyand]

The cheapest node today and for a long time is 28nm. But there are many applications where people are willing to pay more for performance, like processors.

Second there's a debate whether SOI is more expensive once it reaches volume. The claim vary between 10% more expensive , to cheaper , to something in the middle. We'll see.