Who puts a price on the college textbooks. i am in the process of doing some research & wanted to know who?

igns the prices to college textbooks because i called my bookstore @ my college & she said that the bookstore doesn't actually ign the prices (by the way prices of college textbooks are expensive). she said it was something about a marginal cost or something. she really wasn't giving me information that i understood so i wanted to know which people ign the textbooks if the bookstore doesn't & how do they come up with the cost of a particular textbook