Folks, I have posted about this here and on CBO but if you buy a copy of one of my books from anywhere other than the online store I get between £1.50-£2.00 from the sale of a £25 book.
Basically, these book services order FROM the online store at a discount and I have no real say in this other than to remove a book. You get 'free' postage because postage is included in that £25 and that is why after the POD company, the printer and whichever store, sort out their cut I am giving the book away.
Remember the amount of time and work that goes into publishing a 405 pages book -let alone years of research or even tracking down and buying sources. £25 is not an extortionate amount.
PLEASE bear this in mind.