In the newspaper business, it used to drive me crazy if I found a single error after the paper came out. It was as if the whole newspaper was stained in some way by that error. With a book, it would seem even more important to catch every mistake, but book authors don’t necessarily budget the money or see the need for an editor.
A book with mistakes is sort of like a broadcaster with a speech impediment. No matter how good the content, it is lost to the listener as attention is focused on the impediment. The same is true with book errors that catch the reader’s attention. An unedited manuscript might easily average one mistake per page. But that would total 400 mistakes in a 400-page book, and that would seem to be enough to mar an author's credibility with a reviewer or the average reader.
How does an author know what to pay a copyeditor? The problem is that cost is both a function of the hourly rate of the editor and the speed with which the book is read. The reading speed is related to the number of errors in the material, the type of book edited, and the efficiency of the copyeditor.
That’s why I was a bit surprised to learn on page 23 of the Self-Publish-Your-Book Handbook by Joe and Jan McDaniel, owners of Parker-based Bookcrafters, that Amazon.com company CreateSpace charges a flat $160 for copyediting 10,000 words. That means a book of 400 pages and 100,000 words would cost $1,600 to copyedit. A flat rate is surprising because of the huge variability in quality of manuscripts that are edited.
I think that flat-rate-per-word approach is the exception. Most editors have an hourly rate, but it's hard for the author to know how many pages an hour each editor might copyedit. Someone who charges $50 an hour and copyedits fifteen pages an hour would be less costly than someone who charges $25 an hour and copyedits five pages an hour. And of course there's the question of maintaining quality while also maintaining speed.
In their book on page 37, the McDaniels cite a rate on manuscript edits of $35 an hour.
The Chicago Manual of Style doesn't cite a typical hourly rate, but it does provide a time estimate for copyediting a 100,000-word book. It states at section 2.49 (page 71 of the 16th edition) that such a book, “edited by an experienced editor, might take seventy-five to one hundred hours before being sent to the author, plus ten to twenty additional hours after the author’s review.” See http://sheanaochoa.com/editorial-services-3.
However, if you take the assumption of 100 hours for 100,000 words, and you add it to the CreateSpace number of $160 for 10,000 words, the combination translates to $1,600 for 100 hours of work, or $16 an hour. That's less than half of the $35 an hour cited by the McDaniels.
Of course a lot depends on the manuscript. I recently read one history book in which it sometimes took me an hour to copyedit 1,250 words because there was so much fact-checking involved. That's within the range of copyediting speed suggested by The Chicago Manual Style when it talks about 75-100 hours for 100,000 words (which works out to 1,000-1,333 words per hour). On the other hand, I just copyedited part of a fiction book that I was covering at 5,192 words an hour, more than four times faster.
Because of those discrepancies, I like to take a sample, read it with the highest focus and speed possible, and quote a rate for x number of pages based on the sample. Then the author has an idea of what the total cost will be and is not blindsided if the submitted book is particularly tough to edit. It also avoids a situation in which the editor ends up earning less than the minimum wage.
Anecdotal evidence suggests that geographical differences pose another stumbling block to figuring out copyediting rates. For instance, I have one friend in Denver who charges $50 an hour, an acquaintance in Dallas who charges $100 an hour, and a longtime friend in New York who charges $150 an hour. One friend in Bailey, Colo., told me she charged $30 an hour for editing books 20 years ago.
The Editorial Freelancers Association, a national nonprofit based in New York City, cites a rate of $30 to $40 an hour for basic copyediting, but it also cites copyediting speeds of 5-10 pages an hour (see http://www.the-efa.org/res/rates.php). And it notes that the industry standard for a manuscript page is 250 words (while the sample of the fiction book I just read had 375 words a page). At the lowest rate ($30/hour) and highest speed (10 pages/hour), that works out to $120 per 10,000 words, which is lower than the CreateSpace flat rate cited. At the highest rate ($40/hour) and slowest speed (5 pages/hour), that works out to $320 per 10,000 words, which is twice as high as the CreateSpace flat rate.
In other words, there are a lot of variables, but hopefully some of the examples above provide some framework for decision making and budgeting. I personally think the key is for the copyeditor to read a sample first. Then there are no surprises for either party.