The traditional form of self publishing is a mugs game unless you have a guaranteed market. If you were, for example, to write a small book about some historical site and sell it in the tourist shops in that town, you could make a profit. If, however, you try to market a work of fiction or even non-fiction, you are going to run into a stone wall. Very, very few bookstores will even look at a self=published book. Advertising your book and taking orders leads to another problem - delivering your books. You will find that the average cost of mailing a book is about $8-$10. That has to be included in the cost of your book, so if it costs you $6 to print a book, another $1 to advertise it, and $8-$10 to deliver it to your customer, the price is now up to $15-$17 per book, and you have not yet added in your profit, and presumably you want to make a profit.
If you publish a book with a traditional publisher, the cost of the book in the bookstore is around $30. The writer gets 10% royalties - or $3. That sounds outrageous, but it isn't, because the publisher is bearing the cost of printing the book, marketing it, advertising it, delivering it to the bookstores, and the bookstore takes a cut to pay for the rent, the employee salaries, overhead, etc.etc.etc.
If, on the other hand, you self publish an ebook, it can be sold for $3, the publisher takes a small cut, the book store, like Barnes and Noble, takes a small cut, and $2 clear profit goes to the writer. That works - and a lot of writers like it.
One great advantage to an ebook is that you can update it at any time - you can't do that with a traditional book. If something changes, or you want to alter your text, boxes of books sitting around in warehouses have to be trashed and new books printed. With ebooks, you simply upload new text into the book. Wonderful for books that have topical content.
The other point to consider is that the upcoming generation - the teenagers - are already into electronic texting. Most of them do more etexting than they do handwriting (except for school assignments) and much of what they read is in etext format. So they are already accustomed to the format and feel comfortable with it. The old fogies - like me - are not. We've had to learn how to use it, and many older people won't do that. But it's not a problem because that generation is dying out.
So, in my books at least, the coming thing is ebook publishing. There are already some ebook publishing houses -= such as Smashwords - which have layers of books. You can self publish anything and it goes on a general listing. If you want to go in the premium catalogue, your book has to meet the some stringent requirements, as to format, cover, content, etc.
Visit Smashwords and have a look. I think it's great and I've published four books with them. I have also published books with traditional publishers and have self-published two books, so I do have some basis for comparison.