The cost of a developmental editor varies greatly depending on a multitude of factors such as experience, the size and complexity of the project, and the editor's location. Generally, the average rate for a developmental editor ranges from $40-$70 per hour.
However, some developmental editors may charge by the page or project. Average rates for these types of editors are around $5-$10 per page, or $1-$3 per word. Keep in mind that higher rates do not always guarantee better quality work, just as lower rates do not necessarily mean poor quality work.
When looking for a developmental editor, it's important to take into account their experience and credentials. Someone with years of experience and a strong portfolio will most likely charge more than a newer editor who is just starting out.
It's always a good idea to ask for references and samples of the editor's work before agreeing to work together. Additionally, be sure to discuss payment and payment schedules before beginning any work to avoid any misunderstandings or surprises.
In summary, the average rate for a developmental editor can range from $40-$70 per hour or $5-$10 per page. However, rates can vary based on factors such as experience, project complexity, and location. It's important to consider quality of work, experience, and credentials when choosing a developmental editor, and to discuss payment and payment schedules upfront.