The brilliant folks at Priceeonomics wrote about the cost of textbooks for various majors.:
They noted that textbooks for certain majors are particularly expensive--sometimes four times as expensive as the books for the least expensive ones.
They used data from the University of Virginia--all the textbooks for courses in the Fall 2015 semester: nearly 5,000 textbooks from more than 750 courses.
See this chart to see the results. They assume all books are bought new, and students buy all required and optional textbooks.