As you might know, Snow Leopard was the first version of Mac OS to have the Mac App Store, which has since become the only way of installing major OS upgrades. For a user wanting to upgrade from Leopard (OS X 10.5) to Mountain Lion, going through OS X 10.6 becomes a necessary intermediary step in order to gain access to the Mac App Store. Apple was, in fact, briefly giving free copies of Snow Leopard DVDs to MobileMe users to encourage migration to iCloud.
The key here is that you can jump from Snow Leopard right to Mountain Lion (you don’t need Lion first), assuming that your Mac can handle Mountain Lion of course. Apple has all the upgrade details for you to help you get started. So here’s our advice: if you’re still on Leopard, jump to Snow Leopard at least. If you can jump to Mountain Lion, do. And if you haven’t already, consider bumping the RAM up in your Mac to 8GB. It’s worth it.
The $19.99 price is $10 lower than what Snow Leopard retailed for on launch. You can order Snow Leopard by heading over to Apple’s online store.