I'm sure the companies have metrics that go into their reasoning that factor in trade sales. They have so many years of sales data to rely upon so they can know that on a given book, trades will sell at 5% of average monthly rate or whatever the number actually is. They will probably have it broken down by book and be able to compare it to similar books to work out a model of projected revenue and cost. Trust me as a CPA that has consulted with and audited large public companies and am now an internal auditor for a $3B organization that they are very aware of where their revenue is coming from and have spent significant time performing analysis on profit/loss of the book. There is also opportunity cost whenever they publish a book as there is only so many books that they can publish at one time. If they think that they can release a different book that would perform better than this one, it would benefit them to cancel this one for that.