We sum up each Robot's input and output. Depending on the number of Steps you have and how you chain these together (maybe you want to virus scan your media before passing it to encoding & storage Steps).

We found that charging for input & output of each step was the only sensible way to support any kind of file and all possible combinations and workflows, in a sustainable way. That said, we do provide drastic discounts (some bots are either free, or only every tenth byte is counted) in cases where this pricing model would become unattractive.