At this time we can present three ways to provide illustrations for your book.
1) Custom Illustrations: There is nothing better than custom illustrations to make the text "come alive".
Custom illustrations range from $150 to $250 each. You will be working with a professional team to get it right.
2) Student Illustrations: We have been contacting art schools and we have built a partnership with a number of them for students to build their portfolio. We do not feel that anyone should work for free though, and so, the student illustrations about half that of the custom illustrations ($95 each). Also, you have less latitude with students than you do with the professionals in Option 1. In some respects, "you get what you get", when you use a student.
3) Royalty Free Clip Art: We will work with you to find clip art that can work with your book. It works, and basically you are paying the project manager to work with you to accumulate the images. This works out to about $25-$50 per image
I hope that explains your options regarding the cost of the images and helps you decide which best fits your situation.