Before revision:  The theory assumes that customers find a price unfair when it carries a high markup over cost, and that customers dislike unfair prices . Since markups are not observable , customers must extract them from prices.
After revision:  The theory assumes that customers find a price unfair when it carries a high markup over cost, and that customers dislike unfair prices , namely those marked up steeply over cost. Since costs are unobservable , customers must extract them from prices.