At one stage in his career, the American journalist and writer Upton Sinclair wrote 8,000 words of fiction a day, seven days a week. This was because he was a writer for the pulps (you really ought to click this link – it’s only Wiki, but there’s more fascinating stuff there than I could squeeze into a dozen Clutterbucks). A pulp writer, it was said, had to write a million words a year to turn a profit.
And this, bear in mind, was in a genre – or, rather, an industry – in which flimflam and excessive verbiage (“wordage fat”, in pulp parlance) were just not tolerated. You couldn’t pad your story out with lyrical meditations on love and mortality (although you could always just bung in another sex-scene or knife-fight). Everything was stripped to the bone. It was mostly awful, but by god it was punchy.
Raymond Chandler got his start as a writer at Black Mask, the king of the pulp magazines, making his début in 1933 with ‘Blackmailers Don’t Shoot’. There’s a great chapter on this era – as Chandler the soon-to-be drunk succeeded the already-very-much-a-drunk Dashiell Hammett as the genre’s champion – in Tom Hiney’s biography of Chandler (Random House, 1997).
You can explore pulpworld more thoroughly at the excellent Pulp Magazines Project.