Personally, I'm surprised Apple hasn't temporarily dropped its prices to near cost to capitalise on this enforced change by Microsoft. One might think this would be a good time for them to lock in new users to its products.
The OS X 10.9 upgrade was/is being given away free to 10.8 users.
I agree in principle it sounds like a great idea to do so but....
The problem is the business model doesn't really permit it. Since unless its an upgrade scenario (10.8->10.9 excepted), they don't charge for the operating system as such (unlike Microsoft where you can buy Windows off the shelf, or manufacturers pay royalties). With Apple the hardware subsidises the software. The cost of developing and maintaining OS X for desktops/laptops (and iOS for phones and pads) is paid for by the hardware.
Which is one other reason why people saying Apple is expensive are just spouting FUD ..... they use premium parts and don't cut corners in their hardware. On top of that, margins from the hardware go towards the software.
Also Apple probably know realistically that by the time they discount the business/government XP users, the stubborn users, the budget/developing country/"BOAC the Pensionner" XP users,that the number of new users they would gain from temporary agressive pricing is probably limited (in relative terms).
Apple are starting to make some efforts to start catering for those on a lower budget (e.g. the plastic versions of the iPhone 5) ... but they don't want to start cutting corners and going all cheap because that would risk brand integrity. I suspect we will probably eventually see a re-introduction of a plastic option for Apple laptops (and maybe even desktops, but I suspect they're waiting to see how the desktop game pans out in the industry).
Its a bit like saying BMW or Audi should go competing in the Ford Mondeo world. Sure a Mondeo is cheaper and it will get you from A to B.... but the cheapness shows in the parts and construction and it would be tiring to drive on long distance jaunts.
What people could look at doing under their own steam would be to get a WEEE recycling company to buy their computers (or just flog em on Ebay) and use the money from that to contribute towards the cost of buying an Apple.