"The market for textbooks is distorted," argues Phil Hill. "There is absolutely no reason that a digital textbook rental should cost five times what a physical textbook rental costs." I would pause to observe that the use of the word 'distorted' implies there is some 'natural' state of the market, from which I guess we could infer what prices 'should' be, but of course there is no such thing. But I digress. Why do we think textbooks should be cheaper when they're digital. Davide Wiley argues, "When concrete expressions of ideas, knowledge, skills, and attitudes are converted from a physical into a digital format, this changes them from private goods back to being public goods, once again making them easier to share (ie., they are nonrivalrous and nonexcludable). But copyright law "changes these public goods into club goods, once again making them difficult to share." With club goods, you cannot even resell what you have purchased. "Publishers have worked hard to establish a licensing norm and copyright regime that insures that you never own any digital products – you simply license access to them." This prevents any secondary market of used digital texts from emerging, and keeps prices high. So used print texts end up costing less than digital texts.