From the website of publishing service provider, bookbaby:
A great book cover design is your best sales tool. A professionally designed cover will instantly (and attractively) convey the essence of what your book is about.
Basic Cover Design for $399
Deluxe Cover Design for $549
Designing Your Own Cover? Check out bookbaby's checklist.
A tip from Jason Kuritz's presentation at the 2016 La Jolla Writer's Conference: If you plan to have an audio book version, you will need a square version of your cover as well.
Note: The Guild does not post information as endorsements of products. We provide information of general interest for writers and authors to advise of the range of options and opportunities available with the expectation that each person will evaluate them for themselves.