Q: I have already been accepted by an agent, but have not yet signed the contract as I feel self-publishing and owning my own rights is to my best advantage. Rather then make 10 to 12 percent of retail price from book; obviously I would like to see a higher profit margin.
A: Most authors make as much money selling to larger publishers who love their books and get behind it as they do by self-publishing. If the publisher is simply throwing the book out there and seeing what happens, then you are better off self-publishing or finding a publisher who does love the book.
If you are self-publishing to make more money, you are self-publishing for the wrong reason. Most self-publishers lose money. I don't know if anyone has done a study on this but I would guess -- from my experience of talking with thousands of self-publishers -- that 50% of self-publishers break even or lose money. Probably 90% make less than $10,000 via self-publishing.
Don't get sold on self-publishing to get rich or make more money as an author. Choose self-publishing because 1) you want more control, 2) the book needs to get out now, 3) you are a great businessperson, 4) you love to talk to strangers on the phone (and sell your book or yourself), and/or 5) you have an exit strategy or sales plan that is reasonable.