That's a tough question, and it really depends on a lot of variables.
First, it really depends on the scope of the editor's role. Are they simply providing editing advice and guidance or actually doing line editing and providing additional feedback? Some editors also provide additional services such as developmental story structure, character development critiques, and in-depth plot and scene review.
Second, the price of a developmental editor can vary significantly, depending on their expertise and experience. Generally, the more experienced the editor, the more they may charge. Most developmental editors charge between $2,000 - $5,000 for a 115k book, but the price can go up or down depending on their other services and the market and their availability.
It's also important to consider the experience of the editor and the quality of the work. Many authors who are looking for developmental editing need to ensure that they are getting the best quality of work within their budget. To make sure they're getting a quality editor, they should ask potential editors a series of questions, such as:
- How experienced are you with developmental editing?
- What services do you provide?
- What is your process for developmental editing?
- What is the timeline for completion?
- What is your rate and any additional fees?
- What kind of feedback will you provide?
It's also wise to ask for references, as well as for sample edits. This can help to ensure that the quality of work you receive is satisfactory and that the editor is a good fit for your particular project.
All that said, it's difficult to say definitively whether or not $3,500 is a reasonable price to pay for a developmental editor for a 115k book. It's possible to find reasonably priced editors, especially if one is willing to shop around and compare different options carefully. Ultimately, it will come down to the individual author's budget and the services they require.