Patent Cost
Don’t bother about the patent cost at the moment. First, do your research and when you are satisfied that your invention is distinctive cost of a patent enough to get a patent, get yourself a good lawyer who knows how to go about the process of getting a patent. A certain fee is charged by the patents office and certain amount of money your lawyer would want. That’s roughly how much it would cost you.
If your invention is useful, getting it patented would ensure that you could rest assured about your income from the patented product. It would keep coming from the royalties you would get.