Stephen, you’re right, and I think much of the confusion about editing and its pricing stems from the fact that editors offer a range of services (in addition to a range of experience). It might be best to view editing on a spectrum from broad (developmental) to detailed (copyediting and proofreading). And it’s always best to have as clear an idea as you can about the kind of editing you believe you need.
Anyone wishing to pay someone 500 bucks to read their book just so they can be given a short and unhelpful overview is arguably getting what they paid for. Naturally, self publishers and the like can’t really justify the amount they’d have to spend on a real editor of story structure, but it still baffles me that these so called developmental editors exist. That is, unless they have a follow up service after the fact that is actually worth it.
Once you have narrowed your options down to a few editors, five or less for example, set up some initial contact with each of the children’s book editors. Start by contacting them and see if they can answer your core questions via email. Find out if they are willing to chat with you by phone or skype about your project when you are ready to make a decision. Ask for them to specifically identify what children’s book editorial services they will be able to provide.
Obviously there is a big difference. I actually started with screenplays (with some mild success) partly due to hearing that as long as you have a good story, the grammatical errors won’t be a big deal. Well, that was not true. Maybe if a producer liked the story or I was already established but every contest I entered always came back with feedback about the grammatical errors. Even if I won or placed as a finalist, I always received critique on that. Very little is spelling error, it was more about structure, etc.