Another way to look at this is just how efficient the human brain is for the same amount of computation. On one hand, we have racks of servers (1920 CPUs and 280 GPUs) [1] using megawatts (gigawatts?) of power, and on the other hand we have a person eating food and using about 100W of power (when physically at rest), of which about 20W is used by the brain. [1] http://www.economist.com/news/science-and-technology/216…
AlphaGo is still a very new program (two years since inception). It will get significantly better with more training, or, equivalently, it will stay at the same strength while running on much less hardware.
Don't read too much into what one particular snapshot in its development cycle looks like. Humanity has had hundreds of millions of years to maximize the efficiency of the brain. AlphaGo has had two years. It's not a fair comparison, and more importantly, it's not instructive as to what the future potential of AI algorithms looks like.