Interesting blog post here

http://alg.livejournal.com/84032.html?page=2#comments

explaining how publishers work out the profit-and-loss on a book. It's the US version but the principle's the same. You don't have to follow the maths exactly to get the idea.

Emma

Yikes - scary stuff for a new author to confront! But good to know, nonetheless.

There's a further post that she did more recently, about a book where the maths looked similar, but the result was very different. Can't find the link offhand, but if you look at her posts you'll get it.

Emma