A low usage bill can coexist with an expensive operating model. The following is a desk-built illustration dated 23 October 2026. Every input is assumed; none is a client result, supplier quote or market average.
Illustrative monthly workflow
Assume 1,000 distinct customer journeys, each beginning with one four-minute AI call. Of these, 600 complete autonomously, 200 complete after human rescue, and 200 remain unresolved. Successful journeys are counted once.
| Assumed cost item | Calculation | Monthly cost |
|---|---|---|
| AI, speech and telephony usage | 1,000 calls × 4 minutes × assumed $0.18/minute | $720 |
| Implementation allocation | Assumed $6,000 spread over 12 months | $500 |
| Monitoring and operating support | Assumed monthly allowance | $350 |
| Human rescue | 200 cases × 6 minutes × assumed $30/hour loaded labour | $600 |
| Total workflow cost | Sum of the above | $2,170 |
| Unique successful journeys | 600 autonomous + 200 human-rescued | 800 |
| Cost per successful journey | $2,170 ÷ 800 | $2.71 |
If the assumed usage rate falls to $0.10/minute, with everything else unchanged, total cost becomes $1,850, or $2.31 per successful journey. The monthly saving is $320—not the elimination of the implementation, monitoring or human-rescue costs.
The example excludes additional repeat contacts, taxes and lost conversions. An actual model must add repeat-attempt costs while deduplicating successful outcomes. It should also distinguish cash expenditure from an analytical allocation of upfront implementation.
Which benefit should each buyer measure?
These are recommended evaluation rules, not claimed industry results:
| Buyer | Primary economic test | What not to count automatically |
|---|---|---|
| Home-services operator | Additional eligible bookings that become completed jobs, multiplied by contribution after fulfilment costs | Every missed ring as a lost sale; booked revenue as profit |
| Dental or outpatient group | Correct appointments in the operating system, plus reduced administrative work and verified attendance | Every scheduling conversation as a valid appointment |
| Contact-centre operator | Total cost per unique resolved issue, including repeats and human rescue | Containment as resolution |
| BPO transformation leader | Client-approved workflow cost and retained commercial margin | Released staff time as immediate payroll savings |
| Revenue operations buyer | Accepted, eligible opportunities or attended appointments | Dial attempts and calendar entries as qualified pipeline |
For an AI voice agent ROI calculator, keep cash savings, avoided hiring and incremental contribution on separate lines. Compare the proposal with better routing and human answering—not only with an unchanged operation.