In commerce, messaging cost scales with orders
A WhatsApp commerce bill is not driven by how many customers you have. It is driven by how many orders you ship, because each order sets off a confirmation, a dispatch note and a delivery update, and each of those is a conversation Meta bills. Triple your orders and you triple that line, whatever the subscription says.
Anchor the model to order volume
Start with monthly orders today and monthly orders in twelve months. Multiply by the number of transactional messages each order generates. Add cart recovery and re-engagement campaigns from your marketing plan. Add service conversations for queries, returns and exchanges. That is your conversation volume, split by category.