Lester Dent often cranked out 60-70 K words (final copy) a month. Pulp writers were known for their output, whether Brand or Dent or Hubbard. When that's how you eat, and the pay is low, you tend to work hard at it, resulting in large outputs.
Amateurs like myself, with no professional aspirations, crank out much less. My 273rd rate posts take 1-3 hours per post. But when it doesn't flow, I don't post. It'd be a lot different if I were eating on my results....