Assuming that you are knowledgeable about computers and not just looking for the most simple solution, its aesthetics and simplicity. Well engineered up to the very last detail, beautiful, great software, very good hardware.

There is no real competition in this space (unfortunately), so people pay a premium. If you care about how your room feels, let me tell you: it feels a lot better with an iMac instead of some ugly 3rd party monitor. I didn't care about that as much, but now for me it is absolutely worth it.

Also, its a computer for people that don't like to invest huge amounts of time finding the "right" pc - I've started to appreciate that as well.