A WhatsApp budget has three layers, not one
Teams comparing WhatsApp platforms usually compare subscription fees, which is the smallest of three numbers. The second is what Meta charges for conversations, which depends on volume, category and country. The third is the CRM that holds the pipeline, because a shared inbox is not a pipeline. Leave any layer out and the comparison is meaningless.
The layer people forget is the third one
Ask whether your manager could run a Monday pipeline review inside the messaging tool: deal stages, values, close dates, owners, next actions, forecast. If the answer is no, you will buy a CRM as well, and the honest total is both subscriptions plus the connector between them.