I will show you the money.
Although it is possible to publish a book yourself, there are so many steps and skills involved that there really isn't such a thing as free self-pub.
I have an out of print book that I am getting ready to upload and it's going to cost me at least $500, and that's with connections and favors that will save me about half the out of pocket costs.
So, here goes:
You need 2 ISNB #'s - That's $150 each or $300 (you need 2 #'s because you have 2 editions - print and Ebook). Unless you know someone who can give you a discount, there is no way around these costs.
Cover - You need a professional cover. If you do a print edition, there is an extra cost for cover flaps and the back page. This will run anywhere from $50 to $200, although NY publishers routinely pay $600 to $1500.
Formatting/Converting - This needs to be done and will run you at least $100. If you don't have someone who knows how to do this for you, your book will look amateurish and it will be the first thing people complain about, probably in your Amazon review.
Uploading - You can do this yourself, but someone who does it for a living will do a better job. This will cost you anywhere from $50 to $200, depending on how many places you list it.
Copy editing. You should have at least one other set of eyes look over your book. This will run you $100 to $300.
If you are going from a print book to a digital file, that will cost about $100.
So, the eternal question of whether to self-publish or give your book to an epub needs to take into account whether or not you want to lay out $500-$1000. You will probably make that back, but if you go with a publisher, you will start making a profit instantly and not have to worry about all the details that go into publishing.