John Murray II had exceptionally good taste in authors, and was extremely courteous and obliging, but he was also a businessman, with a very nice sense of how quickly a book was selling. He drove a hard bargain, and the more an author needed the money, the less John Murray was likely to pay.

Indeed, with the first few editions of Mrs Raffalds cookery book (one of his best sellers) and some of Byron's early poems, he paid nothing at all.

When Samuel Coleridge offered to do an English translation of Goethe's Faust for 100 guineas, on the condition that he should not have to enter into further negotiations as he was not good at that (as his bargain price shows), John Murray conditioned instead for £100, with the result that we now have no official Coleridge translation of Faust, due to a £4/4d difference between himself and his publisher. (although, Coleridge was on the downhill run by then, so maybe Murray suspected that any amount of money invested in this project would be spent with nothing to show for it.)

On the other hand, Murray burnt Byron's autobiography, in spite of having it gratis and knowing how well it would surely sell, so he was not prepared to profit at any price.

In Jane Austen's case, the last few hundred copies of the first edition of Northanger Abbey and Persuasion were remaindered, so I think the reviews and the advertisements in the literary journals, and his mentioning it to his aristocratic connections, shows that he really put the effort into getting the edition out, and getting as many copies sold as he could. Cassandra got profits on this edition. She might easily have ended up with a loss, if he had been less diligent.

If you compare how Murray behaved after Austen died, with Thomas Newby after the death of his Bronte authoresses (and even before), you can see Mr Murray was hardly a rouge at all.