See this article for information on Audio Broadcast pricing.
What is the pricing for Audio Broadcast?
Are discounts available for Audio Broadcast?
Audio Broadcast is billed on a per event basis. Unlike traditional teleconferencing, Audio Broadcast rates are based on the event size for each event the customer conducts. Rates are auto-calculated based on the maximum number of attendees in the event. Events with less than 25 participants (e.g. practice sessions or dry runs) are free.