This includes editors too. I have had editors who thought I just took a few moments to copyedit, that it wasn't a process that involved much time at all.
From 2013, What does editing cost?
What a copyeditor earns off Copyediting's Tip of the Week series. Also see their Editorial Rates: Not Just for Editing, Not Just for Freelancers. Both links are from 2012, so do seek out more current links, especially if you're checking into rates yourself.
How Should You Charge for Freelance Editing? at Miranda Marquit's blog.
I tend to check the EFA rates guide frequently myself, and I also check other sources as well. For example, I haven't really used per-page rates until this year, so I was researching that.
Generally this is how getting paid breaks down for me: I get an offer from a client for their per-project flat rate, or they offer me their hourly rate; or we negotiate. Some clients prefer hourly rates, some prefer flat rates -- some work with me on what works with their budget and my time.
Bonus: List of errors, aka Common Errors in English Usage from Washington State University... Oh Ghologhosh! This is a great list. I could fall into it for hours.
I'm sure it'll be a much-used reference now that I've found it. 8D Is't not a thing of beauty?