Sierra AI alternatives and competitors in 2026, with pricing

We read each price on the company’s own pricing page. The table links to that page and shows the day we read it.

Our site checks every price again at least every 120 days. If a price gets too old, the site will not go live until someone checks it. That rule is in our code, not just a promise.

Voice AI rates are hard to compare, because each company leaves different parts out. So the table says what each rate includes, and what costs extra.

Sierra charges when its agent achieves an outcome, such as a resolved conversation or a saved cancellation. In most cases an unresolved conversation costs nothing.

The outcome rates are set in a contract and not published. Sierra sells to large brands through its sales team; there is no sign-up form.

Outcome pricing fits when outcomes are easy to agree on. If most of your calls are simple routing or intake, a per-minute rate can be easier to forecast.

PolyAI builds voice agents for large contact centers, with a 99.9% uptime SLA on your phone lines and a 24/7 support line. Its pricing page says ongoing use is priced per minute, but it does not publish the rate. You request a demo to get one.

There is no self-serve sign-up. PolyAI’s team builds and runs the agent with you.

For a large enterprise that wants a managed, high-touch rollout, that is the point.

Retell lists a range of $0.07/min up to $0.31 a minute. Where you land depends on the voice, the AI model and the phone service you choose. Retell bills by the second, and silence and hold time count.

The first 20 calls at the same time are free. After that, each extra line is $8/call/mo.

At the bottom of its range, Retell is a cent cheaper than Komms. If you will tune each part to save that cent, Retell is a good choice.

Extra call minutes are $0.08/min, the same headline rate as Komms. ElevenLabs says it adds no phone fee.

The difference is the AI model. ElevenLabs bills model use separately, on top of the minute rate. Plans bundle minutes: Creator is $22/mo for 275 minutes, and Pro is $99/mo for 1,238.

If you already love ElevenLabs voices, this is the natural pick.

Bland Start is $0.14/min with no platform fee. Build is $0.12/min plus $299/mo a month. The rate covers the AI model, speech and voice.

Bland’s own FAQ says the phone line is billed separately, on your carrier or on Bland’s at cost. Start also caps you at 10 calls at the same time and 100 calls a day.

If you want one company for the whole stack and your volume is small, Start is simple to try.

Vapi hosting is $0.05/min. That is only Vapi’s own share. Speech-to-text, the AI model, the voice and the phone line are billed on top, at each provider’s price.

A usage-only account includes 4 calls at the same time. The Core package is $29/mo and includes 10. Each line past that is $10/line/mo.

Vapi suits developers who already have deals with model and voice companies and want to wire the parts together themselves.

Synthflow no longer lists a self-serve plan or a per-minute rate. Its pricing page says enterprise contracts start at $30,000/yr.

Final pricing depends on call volume, lines, phone setup, integrations and security needs. You get a quote from sales.

For a large team that wants a managed rollout, that can make sense. For a small team, it is a big first step.

Komms covers what a calling team needs:

• A flow builder: each step is a question, and each typed answer leads to the next step.
• Tools the agent calls mid-conversation, like looking up a record or posting to your CRM, and knowledge it answers from.
• Warm transfer to a person when the call needs one.
• Inbound and outbound calls, with English and Spanish voices.
• Test every script in Chat before a call goes out. The same script also runs as a web chat widget.
• Every call is logged with its outcome and the answers the agent collected.

Talk time is $0.08/min, all in: the phone call, the AI model and a standard voice. Billing is in 6-second steps. A phone number is $15 a month. New accounts start with 50,000 free tokens, about 625 minutes, with no credit card.

Bring us your bill: lower prices may apply at your volume.

Where it falls short: at its floor, Retell is a cent cheaper per minute. Vapi’s own share is lower if you already pay for your own model and voice. A premium voice brought from another company bills to you directly.

Build your first agent in about 10 minutes →

Send us last month’s Sierra bill. We will count your minutes and lines, then price the same calls on Komms. Anything we cannot replace stays on the bill, marked as theirs.

If one of the tools above is a better fit, we will tell you.

Send us your bill