Sounds very realistic to me Mike. Lots of us in a similar position. Like you my royalty per book has been steadily falling along with book prices generally for the past ten years or so. A bigger per sale royalty through self publishing sounds attractive. But not if books are supposed to be priced at 99p a pop. And there are those extra costs. I don't think anyone can edit themselves so you will have to find someone to do it for you - and good ones won't be cheap.