WhatsAble bills by unique contacts reached each month, not messages or conversations.
Stay on that tier and go over → +$12 per extra 100 unique contacts (600 → $49 + $12).
Two bills: WhatsAble platform plan + Meta WhatsApp delivery at Meta rates, with 0% markup from WhatsAble.
WhatsAble: Pro at 500 unique contacts = $49/mo + Meta at Meta rates (0% markup) — billed by unique contacts reached, not messages. Go over → +$12 per extra 100.