This leads to a note on printing costs. At the back end, I have a slightly-out-of-date estimator on the main site. (I'm in the process of updating it now; but that involves getting a total of 750 or so quotes from ten different printers and brokers.) This is intended only to give slightly-high ballpark figures to help people see just what the profit margin is for vanity presses.
But that is the back end only. The front end is much more complex: Just how does one know how many pages a manuscript will occupy? In my copious spare time, perhaps I'll convert my stable, well-tested castoff spreadsheet to JavaScript and put it on the main site. For those scratching their heads, the casting off is the process of making that estimate, including allowances for different page sizes, typefaces, leading, paragraph length, footnotes, illustrations, chapter breaks, callouts, forewords, afterwords, author bios, etc. It can be fairly simple for fiction and other simple, pure-running-text books; for fun, try doing a physiology textbook…