Let's assume that it's an excellent book -- well written, entertaining, informative, and let's suppose the RRP is $20. By the time you take off,the publisher's expenses (including editing), the cost of distribution, and the retailer's profit you'd be doing very well if you cleared $4 a copy.
Why not think about publishing on the Net? Expenses are minimal and there's a potential market of zillions.
IF you could PAY for all that it would still depend on the quality of the writing, and I mean if it keeps reader's attention all the way through. It's just like a new movie you'd want to see, but in words. It has to be stupendous for any real money, and you have to pay back what was put into making it, publishing, advertising, your own time, THEN you can look for profit, or is worthless, even if it takes years to become well known. You have to know how to write and about people.