Amazon calculates production costs (number of pages, paper finish, etc) and handling costs (weight, based on number of pages). And probably also makes a estimat

Amazon calculates production costs (number of pages, paper finish, etc) and handling costs (weight, based on number of pages). And probably also makes a estimate of the number of books being sold (given the huge dataset they own, some ML analysis could probably make a fairly accurate estimate). The minimum price is what they charge for the production and distribution, anything on top of that is your revenue.