最佳回答
A WhatsApp conversation is a 24 hour billing window, not a thread, and Meta charges for it because WhatsApp is a paid business product while Instagram messaging is not.
What starts one: the first message in a 24 hour period. Every message inside that window costs nothing extra, however many go back and forth. When the window closes, the next message opens a new one.
What changes the price: who opened it and why. A conversation the customer starts is priced differently from one you start with a template, and marketing templates cost more than utility ones. The categories are Meta's, not the tool's, and they are enforced when the template is approved rather than when it is sent.
What this changes in how you design flows:
- Batch rather than trickle. Five messages inside one window cost the same as one, so there is no reason to compress the conversation.
- Be deliberate about who you open a conversation with. On Instagram an extra follow up is free; on WhatsApp it is a line item.
- Reply inside the window. A reply that lands an hour after the window closes costs a new conversation and needs an approved template.
This is also the reason a handoff from Instagram to WhatsApp should happen when a conversation is worth it, rather than on first contact for everyone.
The Connect WhatsApp article covers number registration and template approval, which are the two steps that take real time.