Active contact
Also called: Active contacts billing, Contact-based pricing
An active contact is ManyChat's billing unit: anyone who sends or receives a message through your account during the billing cycle counts toward your plan.
Why it matters for comment-to-DM
Every person who comments your keyword and receives the DM becomes an active contact for that month. A Reel that pulls 3,000 keyword comments therefore adds 3,000 active contacts, and can push the account into a higher plan for the month, whether or not any of those people buy anything.
Creators call this the success tax: the best month for engagement is also the most expensive month for the tool. It is predictable for an account that runs steady weekly campaigns, and expensive for one that launches occasionally.
Other billing units
Tools bill for different things: active contacts, messages sent, a flat monthly fee, or one payment per campaign. Comparing headline prices without comparing the unit is how a cheap plan turns into an expensive bill.