When I publish a book through 4 Square Books or Amber Skye I usually use the print on demand process which means that a book is only printed when ordered, although if long print runs are needed I use appropriate printers. Using POD, books can be published on Amazon from where they can be bought direct or ordered through bookshops. Authors can order copies in bulk (in any numbers) and sell them themselves or use them for promotional purposes.
An Amazon listing makes a book available worldwide and royalties paid on sales are passed on to the author less a small operating margin. Copies ordered in bulk are charged at cost.