We believe you are asking this question in the context of migrating your onpremise environment to PegaCloud. If yes, we request you to check our service catalog. Even if this may not have answer specific to your question, you can understand the offerings of PegaCloud.
As far as your question is concerned we don't believe Pega Cloud charges based on agents / services that you run. However, for better understanding of the cost, we strongly suggest you to get in touch with our sales team / Account Executive.