  Commercial cloud platforms are a powerful technology for astronomical
research. Despite the benefits of cloud computing -- such as on-demand
scalability and reduction of systems management overhead -- confusion over how
to manage costs remains, for many, one of the biggest barriers to entry. This
confusion is exacerbated by the rapid growth in services offered by commercial
providers, by the growth in the number of these providers, and by storage,
compute, and I/O metered at separate rates -- all of which can change without
notice. As a rule, processing is very cheap, storage is more expensive, and
downloading is very expensive. Thus, an application that produces large image
data sets for download will be far more expensive than an application that
performs extensive processing on a small data set. This Birds of a Feather
(BoF) session aimed to quantify the above statement by presenting case studies
of the costing of astronomy applications on commercial clouds that covered a
range of processing scenarios; these presentations were the basis for
discussion by the attendees.
