This is not a long analytical piece but just an observation I felt I had to write down. Please keep this in mind when you want to comment on these thoughts.
OS X updates may be much cheaper than Windows updates, but OS X versions have a much shorter lifespan than Windows versions. Add to that the costs for updates of other software you use on your Mac and suddenly you are paying way more than Windows users.
Take Windows XP for example. This version of Windows was launched in 2001. More than eleven years later it’s still used by many people and a lot of new software you can still run on XP. As a contrast, take OS X 10.5 Leopard. Launched in 2007. A lot of new apps and software don’t run on 10.5. The minimum OS X these days is often 10.6 Snow Leopard, but sometimes apps already need at least 10.7 Lion to be able to install them.
But it also works the other way around. Say you are still using OS X 10.5 Leopard and you want to upgrade to the latest and greatest Mountain Lion version. And say, you are still using older versions of audio software (like Pro Tools or Guitar Rig) or graphics software (like Photoshop) and you find out that you have to buy upgrades for these software packages as well. A full software upgrade of your Mac is going to cost hundreds of dollars in that case.
If you were a Windows user, chances are much higher that you can still use software packages that are five years old, or even older software, on your brand new Windows 8 computer. There will surely be exceptions, but they will be fewer than on OS X machines.
So not only you pay a premium for Apple hardware (which I don’t mind because I love the design and usability) but software-wise you are paying more as well because you are more or less forced to upgrade faster than Windows users. Will this mean I will switch back to a Windows machine in the future? Who knows. Not in the very near future though. I still love my iMac too much. 🙂