Apple announced that the latest iteration of their OS Mountain Lion sold 3 million copies in four days, making it easily the most successful launch in Apple history. The success of the launch owes its credit to two things: First, Apple has been doing a good job getting their hardware into the hands of consumers lately, but also very importantly, they are offering the software for a paltry $20 on upgrade or new purchase.
Microsoft on the other hand, who has historically charged upwards of $300 dollars for a new copy of the OS, is going to be offering windows 8 professional as a 39 dollar upgrade to existing windows 7 users. This is an important move, and here's why. Apple has always been able to offer their OS at a lower price for a few reasons. One, they've always been an underdog in the OS market by a large margin, and two, Apple isn't just a software company. You need to own an Apple product to install the operating system in the first place, so if you're buying Mountain Lion, that means you've already handed over a chunk of cash for a laptop or desktop.
Microsoft on the other hand has always been a software company, right up until their recent announcement of a proprietary windows 8 tablet. Without a physical product to sell, Microsoft has relied on the initial price of the software and the ubiquity of its use to recoup costs.
With windows 8 however it looks like they're going to be employing a different strategy. Whether or not this is out of fear of people jumping ship or a rush to get everyone onto the same platform because they have other streams of revenue planned for the windows 8 platform, still remains to be seen. Either way it's a much more exciting time for Operating Systems right now than it was during Microsoft's unilateral rule of the 2000's.