Hi Magali,
Your source appears largely biased and isn't entirely accurate. I've got a few disagreements with it.
I'm not going to go into figures, but it doesn't
have to take 18 months to go from sale to print. It does happen in many cases -- but the reason for this is that you have a lot of steps to the publishing process when it is done professionally. Upon acceptance, you usually have initial edits suggested by the editor. This can sometimes be extensive and take some time. There may be quite a bit of back and forth on this. Next, you have copy edits, which is a process that can take a few months to complete. The publisher has to make arrangements to fit your book into their list, work out a promo and marketing plan, and put that plan into action. Let's not forget the design and planning of the cover art and the layout of the book itself. Then you have printing and distribution. Does it take a while? You betcha. However, the quality of the finished product is generally far superior to what you'll find in a self-published book.
Sending a pre-printed/bound book to agents and publishers is not the way to get their attention unless you want to cheese them off and waste their time. The way to get their attention is to
follow their submission guidelines. Most of the time, that means sending them a query, possibly some sample pages, and, most of all, providing them a good, compelling, salable story.
The part about "those with a book..." is a blatantly false statement in this case. Those with a professionally published book (not self-published) have a little more weight behind their queries, particularly if they have a proven sales record, but that's about it. The story you're querying is what the agent or publisher is looking at and going to be selling. Self-publishing does not impress agents or publishers much unless you've sold a ton of books. If you mention that you have published in your credits, the first thing they are going to do is Google it and check, if at all possible, the sales figures, if/where it is available, and who the publisher is.
The thing about publishers not promoting books is also a generality and a falsehood. If you're not Stephen King, J.K. Rowling, or Stephanie Meyer, you may not see your book being promoted in the NY Times. However, that doesn't mean your publisher isn't doing anything for you. Depending on the size, they do anything from giving away advance copies for reviews to internet ads to giveaways to radio/magazine/newspaper spots. It behooves the author to get off their butt and do some of their own promotion, but to say that the publisher does nothing... Sorry, that's a falsehood. Why would they pay money for your work if they didn't expect to make some money off of it to begin with? They HAVE to do some work to make sure it's known, even if it's minimal, otherwise they're simply wasting their investment.
Consider articles
like this and what you can find in the
Snarkives on the subject before going the self-publishing/POD/vanity route. Research what the AGENTS and EDITORS are saying. (Google Nathan Bransford, Janet Reid, Evil Editor, Editorial Ass, Editorial Anonymous, The Rejectionist, The Intern, Pimp My Novel, and many more, to find the truth on the subject -- straight from the source.) Don't take the word of an author -- not even me -- without doing some research of your own. When doing said research, be sure to consider your sources carefully before taking what is said as gospel.
None of this is to say self-publishing is bad or wrong. For some people, it IS the correct route. I suggest you read
this as food for thought.
If you still have questions, let me know.