Earlier quoted context omitted.
Check out the Innovator's Solution, the follow up. It explains why most of the profit (ability to charge your costs plus a premium) was dominated in the 90's by OS's, and not by the now notorious disk-drive companies. Gates probably understood this (how to position yourself not be disrupted) and it's why we're all reading his favorite book - which is great by the way.
And for the other side of the coin -- Jill Lepore's "What the Theory of Disruptive Innovation Gets Wrong" http://www.newyorker.com/reporting/2014/06/23/140623fa_fact_...
http://techcrunch.com/2014/06/30/christensen-vs-lepore-a-mat...