Just as with bandwidth and storage, there are no caps for live stream input or delivery usage on any plan level. You'll simply pay for what you use beyond the amount included with your plan. The cost for additional live input and delivery minutes will correspond with your selected plan. Input cost is higher than delivery cost because your live input must be encoded for optimized delivery.
As an example, an extra 60 minutes of live stream input would cost $9 on the Seed plan, and $6 on the Tree plan, in addition to your monthly platform subscription. However, an additional 60 minutes of live stream delivery would cost $0.60 on the Seed plan, and $0.36 on the Tree plan.