I imagine there are various fixed and variable parts to some of these deals (no inside knowledge). Imagine though that you are selling exclusive rights to your

I imagine there are various fixed and variable parts to some of these deals (no inside knowledge). Imagine though that you are selling exclusive rights to your catalog for a fixed period of time (say 2 years). You would want to maximise revenue while managing risk. As a content provider you may not have sufficient information to figure out what the likely number of views will be in two years times as there are multiple factors you don't have much historical data on (viewer behavior, projected growth rate). Fixed bids are a lot easier to compare than comparing how you think Amazon Instant and Netflix growth rates and customer behavior will change over time.