According to (search engine) Bing, "scientific editing" should be three times as "expensive" as "English editing," while "copy editing" is a lot cheaper.

"Scientific editing" 14,300

“English editing” 56,740

“Copy editing” 1,540,000

These numbers are probably correct, and may be used to "define" what each editing is about. Copy editing is what a journal provides (at no cost to authors). Nowadays, some journals "force" authors to pay for English editing to maintain journals' "images." I doubt any journal is able to provide scientific editing, though many editing companies claim they do so.

Personally, I want to provide scientific editing and I do at least half the time. However, it's a lot easier to say that I provide English editing (and even copy editing occasionally when the authors are big shots), and throwing free (scientific) comments.