So I know there is a quota of supermessages that we need to purchase to run campaigns out of SFMC and consume them according to the multipliers. But what about the meta side? Are there any additional costs billed on meta side as well on top of the supermessages within SFMC? Do we need to keep a line of credit there?
You can no longer use same supermessages for WhatsApp and SMS as for rest of SFMC. These credits are now specific to these channels.
The model for WhatsApp is quite complex, as it is a combination of message type as well as recipients country.
Salesforce will be paying for these messages to Meta, and this cost is covered as part of the above message consumption. No additional costs will be billed directly to you by Meta.