That's an interesting question. people obviously vary greatly in how much work they can get done in all sorts of ways. How much they can get done in an hour, how many hours they can do. They also vary within individuals in depending on circumstances, mood and seemingly unrelated things. I know someone who became extremely productive for a time after exiting a relationship.
I think everyone has experienced extreme bursts of productivity at some point where they think "If I could keep this up: I could work just 3 months a year / complete a degree in 6 months / build this thing in a 3 weeks." The differences between average and awesome, for the same person, are huge.
My guess is that the people who can consistently keep their productivity at the far end of the spectrum are there because of a combination factors, but I am really just guessing.