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Price a voice AI feature by the month, not by the test call

Our voice test for Holt cost under $1, and that is the least useful number in it. At $0.05 a voice-minute plus 15 billed seconds per session start, a 15-minute session is about $0.77 and a daily learner about $23 a month. That figure set the cap. Do this math before any quote.

pricing · holt · case

The answer

Before you put a voice AI feature into a budget or a pricing page, work out what one active user costs per month. Don't go by the test call. Ours cost under $1. The month for one learner who talks every day comes to about $23. The second number shaped the product. The first one would have misled us.

You can get that number in an afternoon, with a few live sessions and some arithmetic. In our view you should have it before anyone sends you a quote with six weeks of discovery in it.

Proof: what we measured in Holt

Holt is our language-learning product. We added a voice module for spoken practice. It is switched on now and being tested with a small group of learners, not opened to everyone. In a spike before the build, we ran three live test sessions against the voice layer and wrote down what they cost.

The rate, from our spike report dated 2026-10-06:

voice layer       $0.05 per minute, billed per second
session start     +15 billed seconds, every session
3 test sessions   under $1 total

That "under $1" is the number that makes voice feel cheap. It tells you very little about the product. Here is the month:

one session       15 min + 0.25 min (start) = 15.25 min
                  15.25 x $0.05            ≈ $0.77

one daily user    $0.77 x 30 days          ≈ $23 / month

About $23 a month for one learner who uses the feature every day, before hosting, support or margin. That is why the module has a limit of 15 minutes a day. We didn't pick the cap for pedagogy and then cost it. The cost set the cap.

Why the test call misleads

A test session costs cents, so it reads as "voice is basically free". The cost of a voice feature isn't a session, though. It is the rate times real use, and real use is the part you don't see in a demo. Our view: any voice estimate that stops at the per-call price is still unfinished.

This isn't only our problem. In an r/speechtech thread, a builder asked what a 10–15 minute voice AI conversation actually costs. Other builders answered with everything from a few dollars for a five-minute call to $0.06 a minute after about 400 calls. That is a spread of two orders of magnitude for the same question. We don't read that as anyone being wrong. Cost depends on the stack, the scenario and how long the context grows. So a vendor's pricing page can't price your feature. A measured unit from your own scenario can.

How to run the same arithmetic

This is the template we use. It fits on one screen and needs three inputs you can measure in a test.

rate_per_min      what the voice layer bills per minute
start_overhead    billed time added per session, in minutes
                  (we had 15 s = 0.25 min)
session_len       how long a real session runs, in minutes
sessions_per_day  per active user
active_days       per month (30 for a daily habit)

cost_per_session  = (session_len + start_overhead) x rate_per_min
cost_per_user_mo  = cost_per_session x sessions_per_day x active_days

Then run it at the usage you hope for, not the usage you fear:

Holt, cap 15 min/day           ≈ $23 per daily user per month
same rate, 30 min/day, no cap  ≈ $45 per daily user per month

The second line is our own extrapolation from the same rate. It shows why a cap is a pricing decision as much as a product one. We think the users you most want are the ones who blow through an uncapped plan.

What the price sheet doesn't show

The same three test sessions showed something more useful than the bill. Behavior is what broke, not price.

failure in the test                     change in the design
--------------------------------------  ------------------------------------
first spoken correction read back a     a correction is one "said -> better"
whole corrected paragraph               fragment, 12 words or fewer

role-play character ignored a           help with words moved to a
"how do I say..." request               separate tool

persona's grammatical gender must       persona gender checked against its
match the voice                         voice

None of these is on any rate card. In our view, each would have cost more than the voice minutes if a learner had met it first, and that is where the real work on a voice feature sits: testing it on odd turns until it stops doing silly things. The arithmetic takes an afternoon. The behavior takes iterations.

A neighboring r/AI_Agents thread, about an operation handling 600–800 calls a day, asks the next question. What does voice AI cost when it gets things wrong in production, on top of the per-minute rate? We think that is the right second question. It is also why we measure behavior in the same sessions as cost.

The $32k quote

On 6 October 2026, a thread in r/AI_Agents described a quote a two-location HVAC business had received. The agent was meant to answer missed calls and book jobs into a calendar. The quote was $32k, plus a six-week discovery phase before anything was built. The advice in the thread was to ask the vendor to split the quote into the build and the monthly cost to run it.

The arithmetic above produces that monthly line. If a vendor can't give it to you, our reading is that they haven't measured their own scenario yet. The thread's author is fair about the exceptions, and so are we. A legacy system with no API, or healthcare with compliance rules on every call, really does make the job bigger. For the plain "answer, check the calendar, book" case, we think the run cost should be a number on the quote, not something to find out later.

FAQ

Why not just quote the test-call cost to the client or the board? Because it describes a demo, not a product. Our test sessions cost under $1. One daily user at a 15-minute cap costs about $23 a month. The gap between those two is your pricing decision.

Is $0.05 a minute what voice costs in general? No. It is what our voice layer billed in our test. Builders in the r/speechtech thread reported anything from a few dollars per five-minute call to $0.06 a minute. That spread is the reason to measure your own scenario.

Does a usage cap hurt the product? It is a trade-off, and we name it. Without a cap, the same rate at 30 minutes a day roughly doubles the monthly cost per user. Holt's 15-minute daily limit comes straight from that arithmetic.

Is Holt's voice module live? It is switched on and being tested with a small group of learners. We aren't promising a date for everyone.

What should I ask a vendor quoting a voice agent? Ask for the build and the monthly run cost as separate lines, with the per-session unit and the usage it assumes. In our experience, that one split tells you most of what you are paying for.

A related case

Holt is where this arithmetic came from. It is our language-learning product, built on a knowledge graph instead of levels, and voice practice is the newest part of it. Try it at holt.il-ob.com. The short version of this piece, one slide per step, is here: {{anchor_url}}.

If you have a voice feature worth building, we'd like to hear about it.

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