This is sort of amazing: BetaNews’s Joe Wilcox has blogged about an NPD report that says that in June, 91 percent of dollars spent on computers costing over $1000 went to Apple. (I think the figure just covers sales at retail stores, not via the Web and other venues.) Windows still ships on 90 percent of computers, but it dominates in the sub-$1000 realm and on corporate machines–two areas that Apple has strategically chosen not to take seriously.
In other words, both Microsoft and Apple have operating system monopolies in the areas where they focus. (Microsoft would presumably be happy to grab more market share in $1000-and-above systems, but the pricing dynamics of the PC market make that more or less impossible.) For all the debate about Mac vs. PC, you could argue that the two platforms effectively don’t compete with each other any more than Chevrolet and Audi do.