The graph, although interesting, tries to compare devices which are not comparable. For one, the relative price of the various "computers" is very different, I have no doubt that if the Apple II cost the equivalent of 400 USD when it was launched way more people would have bought it. Then comes the intended usage. Apple II had a very limited use (either pure office work, or some nebulous programming). What is today the use of mass spectrometers in the general population? Pretty abysmal. They are very useful devices, though (especially if you watch NCIS). The iDevices graphs have roughly the same slope, the iPhone being also a phone (which adds functionality = expected increased consumption). So all in all the results are not that surprising.