Hitch, I don't think anyone here is arguing that an author shouldn't make every effort to make the book as good as possible - but the fact is that competent professional editing costs serious money. As it should. It takes lots of time and lots of skill, good editors well and truly earn their money.
But that money is an obstacle. If you don't have it, you have to find other ways to achieve a good result, which generally means relying on the kindness of others. I wasn't aware that critique groups would be considered useful for editing tasks. I've had many people read over my manuscripts, but the fact is that only a couple of them have the skill and attention to detail required for the job of proof reading - let alone any other facet of editing.
Yes, we should try to make our books as good as the big publishers. On the other hand, most of us aren't trying to sell our books for $10+ each, and we'd be foolish to try. Most consumers, whatever the product, make an automatic allowance with regard to cost. Yes, there are some that think a 0.99c ebook should be every bit as good as a $10 ebook in terms of production quality, but this isn't the rule. Which is not supposed to suggest that the author of the 0.99c book can get away with mistakes on every line, but does suggest that some handful of errors spread through the 100 pages (or whatever) may be forgiven - because, let's face it, even the big publishers let books through with some mistakes.
There will always be many out there willing to upload they're latest effort after spending a whole week,

, typing it out, that isn't going to change any time soon (or, probably, at all). Whether you've spent thousands producing your book, or spent months doing everything you can to make your manuscript as perfect as you can, you are still faced with that reality. That, at the end of it all, your book may disappear into the mire of newly released work.
Good editing is critically important if you hope to ever escape from the mire, but let's not fool ourselves that good editing means your book will sell. So the question of cost definitely does come into it: Just how much money is a person able (let alone willing) to invest in this gamble?