Okay, so I'm an editor and writer (and narrator, by the way), so I've got fingers in every pie here. Bear with me, if you're interested.
There are two kinds of editors - and I'm both.
One is an editor who is an integral part of the author's workflow. For example, I work with several writers who write and publish fast, and they ask me to polish and fine-tune their completed MS while they get on with the job of writing something new. It's not lazy or slapdash, it's simply that they recognise the point at which further editing on their part is less beneficial than starting new material. I'm going to fix it anyway, and there is a lot of faith and understanding in that kind of working relationship. Basically, I highlight the "big" problems for them to fix, and they generally accept my nuts-and-bolts editing without spending too much time checking them.
The other editor is someone who's asked to correct and improve a manuscript from an author who admits they don't know the finer points of writing, and the author is also hoping to perhaps learn, or improve, from that input.
Editors are never teachers, mentors or some kind of "judge" who needs to approve of your book. You work WITH an editor, and if you're ever apprehensive of their feedback or opinion, you're working with the wrong person.
The "kind" of editing provided is an endless debate. Yes, development editing is what it is, but other arguments comparing line, substantial, copy editing ... mean little because each individual editor approaches the role differently. The only thing you can do is ask any editor exactly what they'll do for a specific fee. Forget about any labelling. However, bear in mind that some editors will draw a line at the advice they'll give because you have to assume that process has been done. Meaning, if you're doing a proofread and some of the writing is terrible, it's sometimes prudent to assume the MS HAS been edited. The errors you're seeing have been identified, considered and approved by someone else. It's just not ethical to say, "Hey, did you catch this misplaced modifier?" and to risk for the author's response to be, "Bloody hell, I paid $2k for an editor any they missed it?"
An editor should never change an author's voice - ever. But if they think the voice doesn't work, or is seriously flawed, that should be explained.
The only times I ever significantly rewrite any passage in an MS is when it's blatantly the best means to demonstrate the original problem. I could write 2000 words in a Track Changes Comment trying to explain, or rewrite and say, "It needs something like this..."
Editing a writer's voice, style, meter, tempo and content has nothing to do with content. That's your job. If you need an editor to decide what should and shouldn't suit your genre with regards to content and voice, you're not doing YOUR job. But yes, an editor familiar with terminology and conventions in some genres is necessary.
Pet peeves as an editor?
Excessive exposition ... authors who feel compelled to over-describe every day-to-day action in exhausting, repetitive detail as if they're concerned a reader will complain, "Hey, he can't be in the car! He didn't open the door! And what colour are his shoes?" Readers prefer to fill in the gaps in favour of fast, tight writing. They want to know who shot who, not the colour of the sniper's socks.
Sample edits - I've learned my lesson. People ask for samples and I provide in-depth, considered, time-consuming samples ... and they use it as a freebie how-to lesson on ways to fix their book. Don't be surprised if an editor holds back a little, or is a bit unclear of the processes they're recommending, because too many authors ask for samples as a means to get free MS assessments.
By the way, around $110-$130 per 10K words is about right. People spending "thousands" either have large MS's or are being ripped off. But ultimately, you'll never really have an understanding of what it's like to work with any editor until you've done just that - work with them. Hopefully, you don't have a bad experience. Just don't accept "good enough" either.
That's my (Australian) two cents worth.
