The cost of a line edit depends on a number of factors, including the complexity and length of your project, as well as the nature of the feedback you're requesting. Generally speaking, line edits are priced by the hour or by the project.
If you're working with an experienced editor, hourly rates can vary from $25 to $100 per hour, depending on location and experience. Higher rates often accompany requests for more intensive feedback and the assignment of special tasks such as checking facts or proofreading outside resources.
If you're working with an editor on a project basis, it's a bit more difficult to calculate the cost up front. Typically, line editors offer a quote for a project based on their experience and by assessing the amount of work required. This can range from a few hundred to several thousands of dollars, depending on the scope of the project. If a project has a tight deadline or requires very specific feedback, the cost of the editing could be higher than usual.
Overall, the average cost for a line edit or to hire a line editor depends on the size and scope of the project. No two projects are the same, so it's important to speak to an editor and assess the cost of services that are suited to your requirements before committing to a project.