I'm trying to understand the Transcoder pricing structure and how it would apply to my case... The pricing page states that Transcoder is priced based on "streams per month", and in my case, we have an arbitrary number of user-initiated short-lived sessions (lasting anywhere from 10 min to maybe 2 hours at most). Basically, the end-user might start an event (somewhat similar to the Google "hangout") and then stop it whenever they please. We don't know how many events/streams will be running ahead of time, all we know is the average stream duration (above). In this situation, how do we estimate the Transcoder budget?