Usually the last piece of the book to be prepared is the index. It is vital for most nonfiction books to have an index because it makes them much more user-friendly. Readers can find just a particular topic and not have to skim through a book to find it. If you want your nonfiction book to be taken seriously by readers, distributors, and bookstores, you must include an index.
The author can either outsource the creation of the index to a professional indexer or do it herself with the help of the book designer. Book design software programs can create indexes, but the author must first decide which terms and phrases belong there, and this may not be easy to do. Indexing is very time-consuming, and unless you’ve been trained to do it well, it’s best left to professionals.
It’s important to note that traditional publishers will outsource indexing for you, but often the author pays for the cost of indexing out of the first royalties.
An index can cost from $500 to $1500, depending on how many terms there are. The more technical and longer the book, usually, the higher the cost of indexing.