One of the classics of English Socialist writing before the Bomb—not in terms of "literary merit," of which it has about the same as any other Ingsoc pamphlet, but in terms of its ultimate influence and value as an exemplar—has gone through 111 editions since initial publication in 1913 (or 1914, depending upon your definition of "published"). The total payment to the author and his family since then has been the magnificent sum of £25. And unlike so many of the "informationwantstobefree" yoyos, the family isn't exactly independently wealthy.
What's rather interesting is that nobody has commented on the irony of HarperCollins, which is to say the least unfriendly to socialist thought, being the publisher that has persisted in exploiting this socialist work for its own profit. The paperwork described in the Guardian article sounds more like a tin-siding sale than a publishing contract—and was probably the product of a very similar sort of transaction.