For black and white 6x9 pages are Riso inkjet printers the cheapest to run? Do they make a bw unit that collates? Is it better to print 12x18 and cutting it down or just printing 6x9s on a riso? How many pages can the drum hold? What happens if book #1 is on drum #1 and book #3 is on drum #3, do you swap drums? Are there better alternatives to a Riso? Is it really cost of ink and drums? There are too many riso models to make sense which one is cheapest.