"If $3 million a year seems high, remember that we're talking about the limit case: the case where you not only have zero leisure time but indeed work so hard that you endanger your health."
And his upper limit for hours worked was 2x that of a corporate employee. Taken literally, this could be 80 hours per week, or 16 hour days. PG is not advocating this lifestyle in his essay. He's saying that it's theoretically possible but at the cost of your good health. Arrington says to hell with your health: quit the whining and work through the pain. This is not an upper bound but in fact an average that he's trying to push.
That's why I despise the Arrington article but don't take issue with PG's.