Oh Boy! What I can say?
I had a similar experience in 2017 for my first ebook. I was negotiating with one of these online book brokers, and I just could not seem to get a straight answers out of them. I passed my email communication to my editor, and she thought they were going to "nickel-and-dime" me, which was the same conclusion I had come to. It was time to cut ties with this company before any money got moved their way.
My editor took Amazon. I took Kobo. We moved the document from WORD to the EPUB versions.
It was not that difficult. But still somewhat tedious. Maybe 1 to 2 hours.
There might be a college kid in your part of the world who needs a little extra cash and has some software savvy. Here is what you need to get ready:
1) Word document
2) Cover (I believe they prefer PNG, but get a GIF and JPG version just in case).
3) ISBN. I believe your current publisher has already done this.
4) A 50-word intro to your book.
5) A 300-word intro to your book. Both can be cut-and-paste as needed.
6) Banking info. Your college kid can get you to that page, you enter the numbers from your check.
I would say $200 would be sufficient for that person to go through this learning curve for you. You should be around because there are several rabbit trails to navigate through, like pricing your book and which Amazon affiliates to use. There might be some other things that need to be entered; if you are there, you just tell your computer nerd what to do.
One to two hours.
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Since then, I have learned that these ebook publishers do not do much editing or promotion. They more or less just go through the same process as I have, putting the book on several platforms.
I tried to put my book on Apple IBooks, but the software was too much. Just Amazon and Kobo.