The University of Westminster began collecting and analyzing vendor usage reports since starting their e-book collections in 2004. They have used the results both to monitor the use of the collections and to calculate basic cost-per-use metrics that have informed decisions on whether to renew particular resources. In 2008, they sought to extend the application of usage data by using it to compare the value for money offered by different e-book business models. This article reports on two of these analyses: The first compared a range of options from a single supplier, and the second compared business models from two different suppliers. Although both analyses focussed on e-books, each required a different approach to reflect the differences in business models. (Contains 1 figure and 1 table.)