Voice AI Agency ROI Model: Build Your Own Earnings Calculator
A voice AI agency's monthly profit follows one equation: (clients times retainer) plus per-minute markup, minus your platform fee, minus usage at $0.12 per minute, minus your own overhead. On Trillet's Agency plan ($299 per month, 300 minutes included, as of August 2026), a single client on a $400 retainer already covers the platform fee, and gross margins on a modest book commonly model out above 80 percent before your labor. This article hands you the model itself rather than a fixed snapshot: define each input, plug in your own numbers, and find your break-even client count.
Every earnings figure below is explicitly illustrative. There are no named agencies, no "we earned $X" claims, and no audited benchmark. The point is a method you can trust because you can see every assumption and change it. For the full resale model behind these numbers, start with the white-label voice AI platform guide for agencies.
The core ROI model: one equation, five inputs
The whole model reduces to a single line: monthly profit = (N x R) + markup revenue - platform fee - usage cost - overhead. Five inputs drive it, and every other figure in this article is derived from them.
- N: number of active clients.
- R: average monthly retainer per client.
- Markup revenue: any per-minute margin you bill above your $0.12 cost (optional, covered below).
- Platform fee: Trillet Studio $99 or Agency $299 per month (as of August 2026).
- Usage cost: minutes above your plan's included pool, at $0.12 per minute.
- Overhead: your time, or a virtual assistant, or software you add.
Two of these are fixed and knowable (platform fee and the $0.12 usage rate). Three are yours to set or estimate (client count, retainer, and how you handle minutes). A working model treats the knowable numbers as constants and stress-tests the three you control. That is the difference between an ROI model and a revenue guess.
Modeling revenue: retainer plus minute markup
Agency revenue has two levers, not one: the flat retainer, and an optional per-minute markup on usage. Most guides only model the retainer, which understates what a well-structured account earns.
The retainer is your predictable base. Agencies commonly set this between $300 and $600 per agent per month, tiered by vertical and value delivered. A ten-client book at a $400 average retainer is $4,000 in monthly recurring revenue before a single minute is metered.
The minute markup is the second lever. Because your usage cost is $0.12 per minute, you can bill clients a higher per-minute rate and keep the gap. At a $0.20 client rate, that is $0.08 per minute of pure markup, so a client running 600 minutes a month adds about $48 beyond their retainer. Trillet's Agency plan supports custom minute markup natively, and because the first 300 minutes across your account are included in the fee, your effective cost on early minutes is even lower than $0.12. Markup scales with heavy users, which is exactly where a flat retainer would otherwise erode your margin.
What to do: decide per client whether minutes are bundled into a flat retainer (simple, predictable) or metered with a markup (protects margin on high-volume accounts). Model both and pick per client, not per agency.
Modeling costs: platform fee plus usage
Your cost side has only two moving parts: a fixed platform fee and variable usage, both knowable in advance. That predictability is what makes the model reliable.
The platform fee is $99 per month for Studio (up to 3 client workspaces, 100 minutes included) or $299 per month for Agency (unlimited workspaces, 300 minutes included), with 20 percent off annual billing and a 28-day money-back guarantee, as of August 2026. There are no setup fees and no contracts.
Usage is $0.12 per minute for every minute above your plan's included pool. Transferred-call minutes, where the AI hands off to a human, are billed at $0.05 per minute. To model usage, estimate average minutes per client per month (250 to 400 is a reasonable planning range for an inbound receptionist agent), multiply by your client count, subtract your included pool, and multiply the remainder by $0.12.
The honest takeaway is that usage is rarely the number that decides your profitability. At 2,500 total minutes on the Agency plan, usage runs about $264 a month against thousands in retainer revenue. The fixed fee and, far more, your client pricing and your own hours are the levers that matter.
Gross margin and break-even: how many clients to profit
Gross margin on a healthy book models above 80 percent before your labor, and break-even usually lands at one to two clients. Gross margin here means (revenue minus platform fee minus usage cost) divided by revenue. It deliberately excludes your time, because your hours, not per-minute cost, are the real constraint once you scale.
To find break-even, compute each client's contribution: retainer minus that client's usage cost. At a $400 retainer and 250 minutes billed as overage, contribution is $400 minus $30, or $370. Divide your fixed costs by that contribution. Against the $299 Agency fee alone, break-even is 0.81 clients, so the first client covers the plan. Add $250 of monthly overhead and break-even is ($549 / $370) = 1.48, so two clients cover the whole operation.
The Studio-to-Agency crossover is more subtle than it looks. Studio includes 3 workspaces and charges $15 per additional workspace, so on pure subscription arithmetic, Studio plus add-on workspaces stays cheaper than the $299 Agency fee until roughly 16 clients: $99 + (N - 3) x $15 = $299 solves to about N = 16. In practice, most agencies move to Agency far sooner, at three to five clients, because Agency adds unlimited workspaces without per-seat fees, 200 more included minutes, custom minute markup, and a direct line to engineering. What to do: let features, not fee arithmetic, trigger the upgrade; the math says you can wait, but the workflow usually says go earlier.
A worked example you can copy (illustrative)
Here is the full model with one set of hypothetical inputs, so you can replace each number with your own. These figures are illustrative planning numbers, not a promise.
Inputs (illustrative):
- Plan: Agency, $299 per month, 300 minutes included, $0.12 per minute overage
- Clients (N): 10
- Retainer (R): $400 per client
- Minutes per client: 250 per month (2,500 total)
- Overhead: $250 per month (your time or a VA)
- Minute markup: none in this variant (minutes bundled into the retainer)
Calculation:
- Revenue: 10 x $400 = $4,000
- Usage cost: (2,500 - 300 included) x $0.12 = $264
- Platform fee: $299
- Gross profit (before overhead): $4,000 - $299 - $264 = $3,437 (about 85.9 percent gross margin)
- Net after overhead: $3,437 - $250 = $3,187
Now test the input that moves the model most. Holding client count at 10 and varying only the retainer shows why pricing dominates:
| Retainer per client | Monthly revenue | Gross profit | Gross margin |
|---|---|---|---|
| $300 | $3,000 | $2,437 | 81.2% |
| $400 | $4,000 | $3,437 | 85.9% |
| $500 | $5,000 | $4,437 | 88.7% |
A $100 change in retainer moves gross profit by $1,000 a month at this book size, while the $264 usage line barely moves. That is the model's central lesson: what you charge, and how many clients you keep, decide your ROI far more than per-minute cost does. Explore Trillet White-Label pricing to lock in the two fixed inputs, then build the rest of the model around your own retainer and client-count assumptions.
Turning the model into a decision
A model is only useful if it changes what you do. Once your numbers are in, three decisions follow directly. First, set your minimum retainer above the point where a single client is unprofitable after your overhead; on the figures above, anything below roughly $80 per client fails that test, so the real floor is set by your time, not the platform. Second, decide your minute policy per client, metering high-volume accounts and bundling low-volume ones. Third, revisit the model quarterly as your client count and average minutes drift, because the crossover points and margins shift with them.
The white-label platform for agencies supplies the two constants this model depends on, a native stack with predictable $0.12 per minute usage and a flat monthly fee, so the only variables left are the ones you control. If you would rather see finished figures at set client counts than build the model yourself, the AI Voice Agency Economics: Real Numbers at 3, 5, 10, and 20 Clients breakdown is the companion snapshot to this methodology.
Frequently Asked Questions
How do I calculate ROI for a voice AI agency?
Use one equation: monthly profit equals (clients times retainer) plus any per-minute markup, minus your platform fee, minus usage at $0.12 per minute, minus your overhead. Fill in the three inputs you control (client count, retainer, minutes per client) and hold the two fixed ones (Trillet's $99 or $299 fee and the $0.12 usage rate) constant. The result is a model you can stress-test, not a single number.
What is a realistic gross margin for a white-label voice AI agency?
On a modest book with retainers of $300 to $600 per client, gross margin (revenue minus platform fee minus usage) commonly models above 80 percent, because the cost side is a small fixed fee plus $0.12 per minute of usage. That figure excludes your own labor, which is the real constraint at scale, so always model a net figure after overhead too. These are illustrative planning ranges, not guaranteed outcomes.
How many clients do I need to break even?
Break-even usually lands at one to two clients. Each client contributes its retainer minus its usage cost (about $370 on a $400 retainer with 250 minutes), so a single client covers Trillet's $299 Agency fee, and two clients cover the fee plus a few hundred dollars of overhead. Your exact break-even depends on your retainer and how much of your own time you count as a cost.
Should I bundle minutes into the retainer or bill a per-minute markup?
Do both, chosen per client. Bundle minutes into a flat retainer for low-volume, predictable accounts, and meter high-volume accounts with a per-minute markup above your $0.12 cost so heavy usage adds margin instead of eroding it. Trillet's Agency plan supports custom minute markup, and the included-minute pool lowers your effective cost on early minutes.
When should I upgrade from Studio to the Agency plan?
On pure fee arithmetic, Studio plus $15 add-on workspaces stays cheaper than the $299 Agency plan until around 16 clients. In practice, most agencies upgrade at three to five clients for the features: unlimited workspaces, 200 more included minutes, custom minute markup, and dedicated support. Let the features trigger the move, not the arithmetic.
