  We develop a version of the pi-calculus, picost, where channels are
interpreted as resources which have costs associated with them. Code runs under
the financial responsibility of owners; they must pay to use resources, but may
profit by providing them. We provide a proof methodology for processes
described in picost based on bisimulations. The underlying behavioural theory
is justified via a contextual characterisation. We also demonstrate its
usefulness via examples.
