I thought this was cool, an Illustrated illustration pricing survey by Lisa Maltby. I love the pencil drawn charts and it's informative about all the different avenues money can come from.
Excerpt: 210 illustrators anonymously contributed to this survey in order to start the ball rolling with talking openly about pricing and terms. It also contains insight from art directors from different sized companies and sectors who have anonymously given feedback on working with illustrators*. This survey is not to dictate how illustrators should price their work, but to empower others through knowledge and insight. Please note I am not a statistician and I do not represent a body of illustrators. I have invested in this survey because I believe all illustrators need to have an overview of the industry in order to charge fairly and establish good working terms. This survey is far from exhaustive and will likely provoke further discussion and investigation.