Short answer: Manuscript editing cost normally depends on word count, subject area, language quality, editing depth, formatting requirements, references, and deadline. A responsible provider should review enough of the manuscript to define the scope before quoting rather than promise one price for every paper.
For a useful quote, send the current manuscript, approximate word count, research field, target journal if known, required service level, and deadline. If tables, references, supplementary files, or a response-to-reviewers document also need work, include that information at the start.
Before paying, confirm whether the quote covers language editing only or also structure, journal formatting, references, tracked changes, editorial comments, and a final quality check. Ask whether revisions within the agreed scope are included.
ISI Journal Indexing does not publish a fake universal price because manuscripts vary. We provide a scope-based quote after reviewing the material you want edited.