Calculate additional contribution after all incremental costs—not answered calls multiplied by average invoice value. The following is the desk’s recommended decision model, not an industry return benchmark.
What belongs in the calculation?
| Benefit or cost | Recommended treatment |
|---|---|
| Additional completed work | Count only work above the credible existing-process outcome. |
| Job contribution | Deduct the variable delivery costs associated with that work. |
| Existing callback recovery | Include it in the baseline; do not claim it again. |
| Released office time | Report separately unless there is a specific, achievable cash saving. |
| Supervision and correction | Include staff time and any remedial customer-service cost. |
| Engineer capacity | Cap the forecast at work you can actually deliver. |
| Implementation | Include discovery, configuration, integration, training and internal setup effort. |
| Ongoing service | Include subscriptions, usage, support, maintenance and internal monitoring. |
| Exit | Identify number transfer, exports, replacement setup and supplier assistance charges. |
Recommended formula:
First-year net benefit = additional completed-job contribution + evidenced cash savings − ongoing external costs − internal operating costs − setup costs.
For the first-year decision, build month-by-month scenarios. Do not automatically multiply a busy pilot month by twelve.
What does a realistic break-even test look like?
Illustration only—not market pricing or a forecast: assume £2,400 setup, £650 monthly all-in operating cost, £125 contribution per genuinely additional completed job, and capacity for no more than eight extra jobs monthly. Assume the monthly cost includes supervision and correction, and that the stated job volume persists throughout the year.
| Additional completed jobs per month | Monthly contribution | Monthly benefit after £650 cost | First-year benefit after setup |
|---|---|---|---|
| 4 | £500 | −£150 | −£4,200 |
| 6 | £750 | £100 | −£1,200 |
| 8 | £1,000 | £350 | £1,800 |
Under these assumptions, six additional jobs cover the recurring monthly cost, but at least 82 additional completed jobs across the year are needed to cover the full first-year cost. A positive monthly result is not the same as recovering implementation expenditure.
Which AI receptionist hidden costs deserve questions?
Ask about billable minutes, transfers, silence, voicemail, telephony, messaging, model charges, monitoring and support. These are not interchangeable: Retell’s published pricing, for example, says silence and hold time are billed, and telephony charges can continue after the AI portion of a transferred call ends. (retellai.com)
Also distinguish the AI feature from its underlying subscription. ServiceM8 states that Phone is an additional paid service requiring a paid ServiceM8 subscription. (support.servicem8.com)
- [ ] Obtain low, expected and peak-usage cost scenarios.
- [ ] State VAT treatment and any foreign-currency exposure explicitly.
- [ ] Identify included allowances, overages and minimum commitments.
- [ ] Agree alerts and what happens at a spending limit.
- [ ] Include human fallback costs rather than assuming they are free.
- [ ] Make finance sign off both the conservative case and the maximum pilot loss.
Stage output: a first-year cost workbook and a pilot spending ceiling. If the project only works under optimistic conversion assumptions, narrow it or do not proceed.
Sources cited on this page
- retellai.com ↗www.retellai.com
- support.servicem8.com ↗support.servicem8.com