That linked thread on Anandtech digs in quite a bit. The real physics involved is, of course, more complex than my simple model. Instead of a square dependence,

That linked thread on Anandtech digs in quite a bit. The real physics involved is, of course, more complex than my simple model. Instead of a square dependence, they find the 5th power of the supply voltage. I believe this has to do with how the transistors are designed which creates a lot of wasted current at higher voltages. The square dependence would show with perfect transistors.