Editing Sentry - should I pay for an editor for my book?

Before I published Sentry, I wanted to make sure it was at least readable.  I had (and still have) doubts as to whether it is really the sort of thing people would like to read.  Therefore I went online to find one who would be willing to edit it.  Oh, there are millions of people.  That's the good news.  The bad news is, you'll have to pay for every single one of them, with practically no guarantee of quality.  If you type in "Edit my ebook" into Google, you'll find all sorts of prices.  I reckon it's about $1000 dollars (I live in the UK, by the way) for a 90,000 word novel, but don't quote me on that.  I found out (from more googling) that quite often the editors like you to send in a sample copy of your book, so they can work out how much effort they'll have to put into it.  If, for example, you are a modern Shakespeare, they might ask less.  If, however, you simply bang your knuckles on the keyboard and leave it to someone else to sort out the mess, they will charge a lot more.  Oh, and when I say "no guarantee of quality", that's me thinking back to well-respected/high-ranking Amazon authors whose ebooks are incredibly badly formatted or edited (naming no names).

I have also learned that editors read the book as a normal person might, but with much more experience.  Therefore, they can locate plot holes, where you said something which doesn't happen/does happen later in the book, for example.  They can obviously correct spelling and grammatical errors (you would hope!) and they can even suggest ideas for improving on, or even removing, certain aspects of your book.
Editors can be a very valuable addition to your work, but in both time, but also in money.  Here is the latest article I have read about this subject:

http://blog.nathanbransford.com/2009/10/should-you-pay-someone-to-edit-your.html

Should you get an editor?  Maybe - probably.
Did I use one?  No.
Why?  Because I read another web page (I can't find the link now, it was last year!) that said any writer worth their salt shouldn't need one.
Does that mean I should not use one?  It depends on you.  Do you have the patience to edit a book? (see later in this post!)
Again, why did you not use one, Chris?  Because I read millions of other web pages after that one.  I read advice on how to edit your own book.  Here's what I took from those pages:

1. If a chapter or character does not add to or progress the story, delete it/them.
2. If a book takes time to "get going", consider condensing/deleting the first few chapters.
3. Don't bang on about what's in your head.  No-one likes being lectured.  Just tell the story.  If the characters want to bang on about something, let them, but be sure to gauge the reaction of the other characters, and don't draw it out too much.
4. If you are not good with words, don't write.  

I'm sorry here, but I have read so many negative posts/reviews about writers that think they have what it takes, but can't even string a sentence together correctly, it hurts.  I'm not saying I'm better than them, but I recently read a book (I won't name the title) that I had to put down after the tenth page.  I have never done that with any book before.  Oh, it was an eBook by the way.  Free, thank God, but it seems you get what you pay (or don't pay) for.  It started in the middle of nowhere, with a character who just moved around listening to things and being scared, with bad punctuation, with bad grammar, and with no discernible storyline...the list goes on.  It's this kind of crap that stops people with talent from selling a single book, as they get lost in the mire.  Amazon currently holds over 110 million books, for example.  If I am one of them, (the crap ones, I mean) then I apologise, and will retire after a sufficient amount of negative reviews on Amazon.  If not, I will take the moral high-ground and ask everyone to please think before publishing!

So, with all that aside (and three deep breaths taken), what did I actually do to make sure my book was worthy (in my eyes, of course...we'll come to that in another post) of being read by others?

Answer:  I read it, and read it, and read it, and then I had a beer.  And then I read it some more.  In all, I read it through, COMPLETELY THROUGH, from cover to cover, 7 times!  Oh my god.  It took 9 months.  When I was writing it (and under the influence of alcohol on several occasions), I thought I was writing a new Asimov, but, upon sobering up and leaving it for a week, I realised that writing a book and editing a book are two completely different things.

For example, I had said everything I needed to say in the three weeks it took me to write it (see previous post for my "manic episode"), but it was all wrong.  For example:

• Characters said things later in the book which they never would have said at the start.  I'm all for character progression, but if they have multiple personalities across 250/350 pages, that's just wrong, and unbelievable to the reader.
• Plot holes.  They're like Black Holes, but worse.  A black hole will destroy a galaxy.  A plot hole will destroy a writer's profit.  Far worse...
• DON'T TRUST YOUR WORD PROCESSOR!  Simply zipping down, looking for nice red underlines, or nice green ones under words or sentences is not enough!  For example, how wood a processor know weather this is wright or wrong?
• DON'T TRUST YOUR WORD PROCESSOR!  Localizations can sometimes add, or remove, letters you would not use in your native tongue (did you spot the letter in the previous sentence?  I'm English - we hardly ever use the letter "z"!  TURN THE AUTOCORRECT OFF AND USE A DICTIONARY!
• Capitalisation (Oh my god, my browser just tried to change that "s" to a "z"); indents, paragraphs, chapter titles, sub-headings, it has all got to be addressed!

Having said all that, there might well be a case for an editor.  The question is, though, will they charge you more for converting all that lovely formatting to an Amazon eBook, Smashwords or Createspace format!?  Food for thought...

At that, I think I might leave the editing post for now.  No doubt I'll come back to it when I realise (inevitably) that I've missed something really important out.  THAT'S the beauty/secret/difficulty of careful editing!