This is a common thing to hear when people say they won't read self-published books. Traditionally published authors tend to say it the most and the loudest, usually when they are defending their traditional contracts.
Is there some truth to it? Sure. But it's easy to find and avoid them. Just read the reviews on Amazon. Readers are quick to point out books that needed the help of an editor.
So where can an Indie author get editorial help? And how much will it cost? Let me use myself as an example.
Haunted Vampire went through the following process. When I finished the first draft, I let it sit for a couple of weeks before giving it a read-through (on paper), pencil in hand. Then I gave it to a couple of beta readers who gave me excellent feedback. One of my readers said he liked the book but it lacked dramatic tension. I went back and did a thorough rewrite to address that.
Then I sent it to an online critique group http://critters.org for feedback. About ten people responded, with various comments. I incorporated the comments in another rewrite.
Then I had it professionally line-edited.
How much did it cost me? Actually nothing in dollar terms. The beta reading and critique group were free (although I had to critique in return to "pay" for the group's services). The line-editing was a barter service, so that didn't cost me any money either.
See, it doesn't have to cost a lot to get good editorial guidance. The critiques in return did take some time, but it actually helped me as a writer. Nothing teaches you your craft faster than critiquing others.
The next book is going through a similar process. I've done the beta readers and critique group, and now I'm working with all the comments. My rewrite this time is less intense because it's a better story than the first one, and I learned a lot through writing and editing Haunted Vampire.
If you're thinking about self-publishing your own book, don't think you can't turn out a polished product without spending a fortune. You can!