Svelte new iPads aren't the only new thing Apple introduced at its big media event Tuesday. "Today we're going to revolutionize pricing," software chief Craig Federighi said in his presentation. The days of spending hundreds of dollars to get the most out of your computer are gone, he said, showing a slide of Windows 8 and its price, $199. "Today we announce a new era for the Mac, because today we are announcing that Mavericks is free."

And Apple really wants you to have this newest version of OS X — it's already available to download. If you bought your Mac after 2007 and have at least OS X Snow Leopard (the first OS X version with the App Store), no problem: You can get Mavericks for free, in one step, Federighi promised. In the Big Cat era of OS X, you had to upgrade one feline at a time. And, of course, you had to pay for it, though OS X updates have been getting cheaper with each new version.

Cheap is one thing. Free is another. Creating a big update for a major operating system is expensive and time consuming, so why is Apple giving Mavericks — and, apparently, all future upgrades — away gratis? "Free is good," Federighi explained. "For those of us that work on Mavericks, what's most important to us is seeing the software in the hands of as many Mac users as possible."

Apple is sitting on a Scrooge McDuck–size pile of cash, of course, but this isn't a charitable endeavor. The first clue that there could be an ulterior motive here was Federighi's swipe at Microsoft. Here's Gartner analyst Van Baker:

Microsoft is still, at heart, a software company — its forays into hardware have been a mixed bag: The Xbox is a hit, but the Zune (R.I.P.) and Surface tablets haven't exactly been roaring successes. Apple covers both ends, but the decision to give away software seems to plant its flag more firmly in the hardware camp. Once you buy that piece of relatively expensive iHardware, Apple wants you to enjoy the experience — and buy more Apple hardware.

"Traditionally, PC and software makers have made significant revenue from either licensing OS software or using it to attract new customers to purchase hardware upgrades," says Austin Carr at Fast Company. Apple just "blew up that antiquated model." And the biggest benefit from this explosion "could come through the disruption it might bring to Microsoft's business model." Carr breaks out some numbers:

Last year, Redmond brought in $19.23 billion from the Windows division, with 65 percent of that coming from licensing its operating system to OEMs [original equipment manufacturers]. With Apple offering its sleeker, better-reviewed operating system now for free, Microsoft's pricing for Windows... will seem outlandishly high by comparison.... Imagine a corporate IT buyer choosing between purchasing Macs and Windows-based PCs for employees. Certainly, PCs are likely to remain cheaper up front, but now they might seem significantly more costly to maintain over the years. [Fast Company]

In another poke at its old rival, Apple also announced that it is giving away its iWork suite of software to anyone who buys a new Mac or iOS device. That includes Apple's (roughly) Office-compatible versions of Word, Excel, and PowerPoint, plus cloud versions that sync between your computer and iPhone. This "is a direct challenge to Microsoft, which charges between $139.99 and $399.99 per PC for its Office suite of productivity software," says Alistair Barr at USA Today.

Apple's also aiming some not-so-subtle shots across Google's bow. Mavericks is largely about under-the-hood improvements — Apple says you'll have a faster computer with better battery life after you upgrade — but it also includes a souped-up, 3D-capable desktop version of iOS's Maps, plus improvements to Calendar and its Safari web browser. (Federighi demonstrates Maverick's marquee features above; Lifehacker does it quicker.)

Google pioneered giving away software for free, but the less time you spend using Google Earth, Google Calendar, and its increasingly popular web browser Chrome, the less you need Google for anything other than, well, searching the web.

Still, the biggest thing Apple is selling by giving away its operating system for free is... Apple, says Larry Dignan at ZDNet. Cupertino's "real message is that if it can get all customers on the latest software — a model that has worked for iOS since two thirds of users have iOS 7 now — the company gets more customer loyalty."

One note of caution: The Mavericks update weighs in at 5.29 GB. It may be free, but it will cost you some time for the upgrade.