The idea is that Apple uses software to push more hardware sales. If Apple was a software company, you wouldn't see the fantastic and very useful iLife bundle of applications included for free on every new Mac, including the el-cheapo Mini. Instead, they might decide to charge $99 for it, or worse, break it up into pieces and distribute it as separate packages, each with its own price.
Snow Leopard's price also seems to support this theory, especially when contrasted to Microsoft's pricing model. Any "dot-oh" operating system upgrade priced at $29 is simply amazing. And given the fact that you can upgrade a whole home or small office full of Macs for less than the price of an Xbox 360 game...well, that's just a special kind of awesome. The main OS competitor, however, has graciously offered its upgrade, similar in "just fixing stuff and making it run better" nature to Apple's update, at the low, low price of $129. Ouch! At least you can save a substantial amount by buying Microsoft's family pack at a tick under 150 bucks, but that discount will only get you three copies instead of Apple's five. And it's still three times the price of Snow Leopard's bundle!
But I realized something interesting about the whole "hardware company vs. software company" argument. As a Mac convert, I've noticed that I think quite a bit less about the hardware than I do the software. In the PC world I still live in, we talk about processor benchmarks, motherboard options, frontside bus speeds, and other Ambien replacements. However, when I talk Mac, I'm often concerned much more with the software it's running, what OS version is installed, and where I can find a free app to do what I need.