What a shared inbox costs when conversations are metered

The short answer

Conversation metering links your monthly software invoice to how often your customers decide to reach out. Because you cannot control when buyers send inquiries, shipping questions, or repeat messages, your software costs fluctuate unpredictably. A business pays the largest software bills during heavy sales periods, product incidents, or marketing campaigns.

How the meter works

Most shared inbox conversation meters derive from the billing structure of the WhatsApp Business API. Meta groups WhatsApp messages into distinct time windows. When a customer sends an inbound message to a verified business phone number, Meta opens a 24-hour customer service window. Inside that 24-hour window, the business can send free-form replies without paying per-template fees. Outbound notifications sent outside that window require pre-approved message templates and carry per-message fees determined by the template category.

Timeline of a metered conversation window:

Hour 0                Hour 12               Hour 24               Hour 26
  |---------------------|---------------------|---------------------|
Customer says:        Agent answers:        Window closes.        Customer asks:
"Is this in stock?"   "Yes, blue or red?"                         "Blue please."
[ Conversation #1 starts ]                  [ Window ends ]       [ Conversation #2 starts ]

Software vendors place an additional billing meter on top of Meta's network fees. A common vendor rule states that any interaction within a single 24-hour period counts as one billable platform conversation. If the customer waits 26 hours to send a follow-up question, the vendor marks the previous session closed and bills the new message as a second conversation.

Each software vendor writes its own contract definition for what triggers a new billable event. Some vendors set a 24-hour clock. Others count any thread that an agent manually marks as resolved as a finished conversation, meaning a quick "thank you" from the customer two minutes later opens an entirely new billable event. Some run a seven-day window on certain channels. Find and read this specific definition in the vendor terms before signing an agreement.

What counts as a new conversation

Different vendors apply different criteria to start a new billing unit. Common triggers include:

• A customer replies to an old thread after the platform window closes.
• A buyer sends a second message asking for an update on an open order.
• An automated satisfaction survey or bot follow-up reopens a closed thread.
• An outbound broadcast announcement receives an automated out-of-office reply.
• A client contacts your team from an alternate phone number or secondary email address.
• A member of a group chat sends a message, triggering a conversation count for that participant.

The last two vary the most between vendors, and the group chat rule is the one that catches operations teams by surprise.

Why the invoice grows when the business does well

A conversation meter penalizes commercial growth. When a company invests capital into advertising, the resulting customer interest creates inbound conversations. When a product launch attracts thousands of new shoppers, inbound questions fill the queue. When an unexpected winter storm delays delivery trucks, hundreds of worried buyers reach out to track their orders.

Under conversation metering, these operational events increase software expenses. The company pays higher software bills during the precise billing cycles where delivery costs, inventory purchases, or advertising expenses run highest.

This pricing model also introduces bad operational incentives. Support agents who know that open threads trigger overage fees begin closing customer conversations prematurely. When an agent rushes to mark a ticket resolved, the customer frequently replies with clarifying questions, which opens yet another billable conversation.

Three worked examples

These three examples use Trengo's standard published pricing: EUR 299 per month base plan, 10 user seats included, 6,000 conversations per year included, EUR 18 per 100 conversations above the limit, and EUR 30 to EUR 50 per additional user seat each month.

Scenario one: a small desk

A small company employs three people who handle 400 customer conversations each month.

• Staff: 3 people
• Monthly volume: 400 conversations
• Annual volume: 4,800 conversations
• Base contract cost: EUR 3,588 for 12 months
• Overage fees: EUR 0
• Total annual cost: EUR 3,588

The company never exceeds its annual conversation allowance. Even without paying a single overage penalty, the business pays EUR 3,588 across the year, which equals EUR 1,196 per staff member annually just to maintain a shared inbox.

Scenario two: a support team that grows

A customer service department expands its headcount to 12 staff members while handling rising support volume through four quarters.

• Volume progression: 500 per month in Q1 (1,500), 800 per month in Q2 (2,400), 1,200 per month in Q3 (3,600), 1,600 per month in Q4 (4,800)
• Total annual volume: 12,300 conversations
• Base contract cost: EUR 3,588 for 12 months
• Extra staff fees: 2 users above the 10 included at EUR 30 per month = EUR 720
• Overage calculation: the 6,000 conversation limit runs out during month eight. The remaining 6,300 conversations require 63 blocks of 100 at EUR 18 = EUR 1,134
• Total annual cost: EUR 5,442

In December, the team handles 1,600 conversations. The December invoice breaks down into EUR 299 for the base plan, EUR 60 for the extra seats, and EUR 288 for 16 blocks of volume overage. The December bill reaches EUR 647, compared to EUR 299 paid in January, for a team that increased its operational throughput.

Scenario three: a seasonal spike

An e-commerce business employs eight staff members. Message traffic runs steadily for ten months before multiplying during the holiday shopping season.

• Ten baseline months: 700 conversations per month (7,000 total)
• November spike: 2,600 conversations
• December spike: 3,400 conversations
• Total annual volume: 13,000 conversations
• Extra staff fees: EUR 0 (8 staff members fits within the 10 included seats)
• Base contract cost: EUR 3,588 for 12 months
• Overage calculation: 7,000 conversations above the 6,000 limit require 70 blocks of 100 at EUR 18 = EUR 1,260
• Total annual cost: EUR 4,848

By December, the annual conversation allowance has expired completely. All 3,400 December conversations incur overage billing. That month requires 34 overage blocks at EUR 18, generating EUR 612 in volume fees on top of the EUR 299 base rate. The single December invoice totals EUR 911 during the month where corporate cash is already committed to stock orders and advertising bills.

How to audit a pricing page in ten minutes

Before you sign an order form for a shared inbox tool, review their commercial terms using this ten-step audit process:

1. Locate the vendor definition of the term "conversation." It might mean an open ticket, an inbound message, or a rolling 24-hour window, and those three produce very different bills.
2. Find the window length. Some stay open for 24 hours. Some run seven days. Some hold open until an agent clicks resolve.
3. Verify whether allowances reset monthly or annually. An annual allowance masks the cost cliff until month seven or eight.
4. Ask what happens on the exact day you cross the allowance. The software either blocks incoming messages, throttles delivery, or quietly bills the overage to your card.
5. Confirm whether inbound questions and outbound replies both count against the total.
6. Internal team comments and collaboration notes sometimes count as platform activity. Get that in writing.
7. Ask how the software counts group messages on apps like Telegram or WhatsApp. One message in a 20-person group can register as one conversation or as twenty.
8. Read the seat table for permission levels. An accountant or a warehouse manager who only reads threads may still need a paid seat.
9. Look for a second meter on the AI features. Get the contract definition of a resolution, and ask whether a failed bot answer still bills.
10. Check data retention limits and export rights on the plan tier you are buying, not the top one. Review what file formats you receive on termination, as detailed in our guide to conversation history retention.

Always request your raw conversation logs from your current communication tools for the past 12 months before evaluating a new proposal. Vendor sales projections regularly underestimate real customer message volumes.

What a fixed meter looks like

CommunicationOS uses a fixed infrastructure meter rather than a conversation meter. Customers pay for connected accounts, which represents a concrete number an operations team can count and plan for on day one.

Teammates are free on all tiers. Message volume is never metered. On the Team plan, a company pays USD 79 per month for 10 connected accounts with 10 GB of message history stored permanently, as outlined on our pricing page.

The seasonal retailer in scenario three pays USD 948 for the full year on CommunicationOS instead of EUR 4,848 on a conversation-metered contract. Their December bill stays identical to their January bill regardless of how many thousands of shoppers reach out. Infrastructure uptime guarantees backed by financial credits provide additional billing stability, which you can review in our service level agreement.