Our circulation is higher. We have a more scholarly audience. People want to publish articles with us because they know their work will be well edited. Reputation makes a difference. Copy editing errors can be very distracting.
Copy editors are basically freelance.
So if you're looking for a copy editor, get a list of books or periodicals that they've worked for and evaluate those. You need someone good at detail, very focused. Someone distracted by the story or whose mind wanders won't be a good copy-editing candidate. I'm a good writer, a good technician, but I'm not a good copy editor. A few typos won't necessarily kill your chances with me, though I would make note of them in the review.