Just to be clear, acquisitions editors at publishing houses don’t charge fees. If a “publisher” is asking for fees, then that company is not a publisher. It is a printer. Don’t let the growing popularity of hybrid self-publishing units confuse you. Know exactly what you want and go to the right place.
Now, for freelance editors, fees obviously need to be researched. There is no standard, really, because an individual editor’s experience can be very different than the next person’s. In general, though, the lower the rate, the less experience that person has.
That doesn’t mean they can’t do a good job. It does, however, mean they might not be as good at targeting how to change the words on the page. Editing is like cutting a diamond. There are a lot of people who can cut diamonds but you have to cut at the right place and shape it in the right way to achieve the diamond’s full potential. Same with manuscripts!