Editing and proofreading a work are considered essential. When properly done, they can enhance the effectiveness of your writing style or improve the clarity of your ideas. Nothing is worse than having a great quality book that's lost to the reader by excess verbiage.
A lot of self-published authors don't hire an editor. They feel they can edit themselves or save money by finding a friend to catch their mistakes. While this is true that you can D.I.Y. your own English, it is also true that it is generally harder for someone close to a project to see their own flaws and mistakes.
At first when looking at the cost of an editor, the prices can seem staggering. The price of professional editing can vary widely. Usually, traditionally published books go through several rounds of editing.
TYPES OF EDITING & COST
Developmental Editing - consists of manuscript changes or suggestions for "big-picture" issues/ fixes. This includes changes to plot, character, pacing, or overall story. Developmental editors can charge $0.09 per word.
Copy Editing - consists of fixing mechanical issues with your writing. It is meant to bridge the author's intent and the reader's understanding. Usually, this can cost $ 0.02 and 0.04 a word.
Line Editing - focuses on the content and flow of your prose. It concentrates on style rather than mechanics. Typically, line editing can cost from $ 0.04 to 0.09 per word.
Proofreading - is the last major stage of manuscript editing. It involves ensuring there are no spelling or grammatical errors in the final version of your product. Basic proof reading services usually charge $0.01 and 0.02 per word.
To reduce costs, there are many places were you can hire a flat rate editor. Typically, these editors will charge a fixed price for a set number of words. If you have a limited budget, you can try to hire one of these freelance editors on a number of platforms, such as Fiverr or Upwork.
In short, editing can offer a myriad of value and is not one of those things you want to skimp on.