The historical analysis of the cost or price of medieval books is confounded by the quantity and quality of the available evidence. Medieval scholars depend on very small data sets to address this question, and even the data that are available have been stripped by time of key contextual information. In the absence of a reliable empirical approach to the question, I turn to other forms of inquiry. Some of these are grounded in the close analysis of the physical forms of the medieval codex. I am also interested in ideas about value, and about evidence itself, that I find in some of Chaucer’s writing.