  Data are invaluable. How can we assess the value of data objectively,
systematically and quantitatively? Pricing data, or information goods in
general, has been studied and practiced in dispersed areas and principles, such
as economics, marketing, electronic commerce, data management, data mining and
machine learning. In this article, we present a unified, interdisciplinary and
comprehensive overview of this important direction. We examine various
motivations behind data pricing, understand the economics of data pricing and
review the development and evolution of pricing models according to a series of
fundamental principles. We discuss both digital products and data products. We
also consider a series of challenges and directions for future work.
