Are Professional Editors Really Worth It

I’m about to finish my manuscript and keep seeing recommendations for professional editing services. I get that editing is important, but I’m curious do professional editors actually make a noticeable difference in readability, sales, or reviews? Can self-editing or using online tools be enough, or is hiring an expert truly worth the investment? I’d love to hear from authors who have used professional services did it improve your book’s quality and impact in ways you couldn’t achieve on your own?