Decagon vs Sierra comes down to who runs the agent after launch and how you want to pay. Decagon sells per conversation or per resolution and expects your team to iterate on the agent yourself. Sierra prices on outcomes and builds more of the agent for you. Fin is the only one of the three with a public price: $0.99 per outcome, self-serve, on Intercom or on top of another helpdesk.
All three are strong products. The right pick depends on your volume, your helpdesk, how much of the build you want to own, and whether you need a number you can put in a budget before the first sales call. This guide compares them on those terms, then adds a fourth option, Open, for teams that want published per-resolution pricing with voice included.
TL;DR
- Fin publishes its price: $0.99 per outcome, with a 50-outcome monthly minimum when you run it on a non-Intercom helpdesk. Fin Voice is custom-priced through sales.
- Decagon offers per-conversation or per-resolution pricing, quote only. Third-party data puts the median contract around $400,000 a year.
- Sierra prices per outcome and says that in most cases it doesn't charge for unresolved or escalated conversations. No public price; third-party estimates start around $150,000 a year.
- Voice and channels: all three cover voice, chat, email and WhatsApp. Fin keeps voice pricing behind sales.
- Open charges $0.75 to $0.90 per resolution, doesn't bill handoffs to humans, and passes carrier costs through at cost. It fits mid-market and enterprise teams that want voice and messaging on one agent without a six-figure entry ticket.
Decagon vs Sierra vs Fin at a glance
All prices below were checked against public sources on 12 November 2026. Where a vendor publishes nothing, the figure is a third-party estimate and is labelled that way.
| Decagon | Sierra | Fin (Intercom) | Open | |
|---|---|---|---|---|
| Pricing model | Per conversation or per resolution | Per outcome, with consumption pricing for routing-style flows | Per outcome | Per resolution |
| Published price | No | No | $0.99 per outcome | $0.75 to $0.90 per resolution |
| Typical entry cost | Median ~$400k/yr (third-party estimate, Vendr data via eesel) | From ~$150k/yr (third-party estimate, SelectHub via Featurebase) | 50 outcomes/month minimum on other helpdesks | No platform fee listed |
| Escalations billed? | Depends on model: every conversation counts on per-conversation | "In most cases, there's no charge" | Yes, when a configured Procedure hands off | No |
| Voice | Yes ("Voice 3") | Yes | Custom pricing, select customers | Yes |
| Other channels | Chat, email, SMS, WhatsApp, custom surfaces | Chat, SMS, WhatsApp, email, ChatGPT | Messenger, email, WhatsApp, SMS, Slack, social, API | Chat, email, WhatsApp, social, Slack |
| Who builds the agent | Your team, with a forward-deployed Decagon team | Mostly Sierra | Your team, self-serve | Your team, on your existing helpdesk |
| Best for | Large teams that want to own iteration | Large consumer brands that want a managed build | Intercom users and teams wanting a public price | Teams wanting published pricing plus voice |
Pricing model: who pays for what
Decagon pricing
Decagon doesn't publish prices. Its own comparison page says it offers "per-conversation or per-resolution" pricing and that most enterprises choose per-conversation for predictable costs. On per-conversation pricing, every conversation the agent touches is billable, including ones it hands to a human. On per-resolution pricing, the rate is higher but escalations aren't charged.
Third-party figures vary. eesel, citing Vendr marketplace data, puts the median Decagon contract at about $400,000 a year, with a range of roughly $100,000 to $580,000. Treat that as a planning number for a large deployment, not a quote.
Sierra pricing
Sierra calls its model outcome-based pricing. In its words, "Sierra gets paid only when we complete a task for you." An outcome can be a resolved support conversation, a saved cancellation or an upsell, with criteria agreed up front. For unresolved and escalated conversations, Sierra says "in most cases, there's no charge." For greeter or routing flows, it offers consumption pricing based on conversation count.
Sierra publishes no rates. Featurebase cites a SelectHub listing of $150,000 a year as a starting point, and Sierra's own blog admits outcome pricing is more complex to contract and account for than seats or consumption.
Fin pricing
Fin is the transparent one. It costs $0.99 per outcome. On Intercom you also pay for helpdesk seats ($29 to $132 per seat per month on the plans listed on intercom.com). On another helpdesk such as Zendesk or Salesforce, there are no seat or platform fees, but there is a 50-outcome monthly minimum.
Read Fin's outcome definition closely. A resolution is counted when the customer doesn't ask for more help after Fin's last answer. A Procedure that ends in a handoff to a human also counts as an outcome at $0.99. Conversations passed to your team without an outcome are free.
Voice and channels
All three vendors now cover voice, chat, email and WhatsApp, so the question is depth.
- Decagon markets "Voice 3" as its most advanced voice agent and lists 70+ languages across chat, voice, email, SMS, WhatsApp and outbound.
- Sierra runs one agent across chat, SMS, WhatsApp, email, voice and ChatGPT. Its customer list (Gap, SiriusXM, Singapore Airlines, Vanguard) is heavy on high-volume consumer phone lines.
- Fin covers Messenger, email, WhatsApp, SMS, Slack, Instagram, Facebook Messenger and API. Fin Voice exists but is custom-priced and offered to select customers through sales, so you can't model voice costs from the public page.
If phone is more than a quarter of your volume, ask each vendor for a voice reference customer in your language and region before you shortlist.
Time to live
None of the three publishes a standard go-live timeline you can hold them to.
- Decagon says "most enterprises go live in weeks rather than months," helped by a forward-deployed team.
- Sierra doesn't state a timeline on its comparison or home pages. Expect a scoped engagement, since Sierra does more of the build.
- Fin is self-serve. You can connect it to your help center and turn it on without a sales cycle, which makes it the fastest to test.
The real constraint is usually your knowledge base and your back-end APIs, not the vendor. An agent that can only answer questions goes live fast. An agent that issues refunds, changes bookings or verifies identity needs integration work whichever vendor you pick.
Who each one fits
Pick Decagon if you have a large support org, an internal team that wants to tune the agent every week, and budget for a six-figure annual contract. Per-conversation pricing gives you a predictable bill if your resolution rate is still climbing.
Pick Sierra if you're a large consumer brand, phone is a big channel, and you'd rather the vendor own the build. Outcome pricing lines up spend with results, as long as you negotiate the outcome definitions carefully.
Pick Fin if you already run Intercom, or you want to test an AI agent this month at a known price. It's the lowest-friction start of the three.
Decagon alternatives and Sierra alternatives are worth a look if you can't justify a $150,000-plus entry ticket, you need voice on a published price, or you want to keep your current helpdesk untouched.
The fourth option: Open
Open is an AI customer support platform founded in 2023. Its agent, Agent 5, is trained once and deployed across voice, chat, email, WhatsApp, social and Slack. It runs on top of the helpdesk you already have. On Zendesk, for example, it works inside your existing triggers, macros and assignment rules and hands off to a human with a summary when needed.
How it compares on the points above:
- Price: $0.75 to $0.90 per resolution, depending on volume, published on the pricing page. That's below Fin's $0.99 list price.
- Escalations: handoffs to a human aren't billed. Unlike Fin, a handoff never counts as a billable outcome.
- Voice: included on the same agent. Voice runs on top of the carrier you already use, and carrier costs are passed through at cost.
- Proof: FareHarbor's agent handles 87% of support across email, chat and voice.
Where Open is the weaker fit: if you want a vendor to design and run the whole agent for you as a managed service, Sierra's model is built for that. If you already live in Intercom and want everything in one product, Fin is the simpler choice.
How to compare quotes fairly
The headline rate is rarely the number that matters. Before you sign with any of these vendors:
- Get the resolution or outcome definition in writing. Does "no further help requested" count? Does a handoff count? Fin bills some handoffs; Sierra and Open generally don't.
- Model your own volumes. A per-conversation rate looks cheaper until you multiply it by every conversation, including the ones a human finishes. Run the numbers in the ROI calculator.
- Ask for the full first-year cost. Platform fees, implementation, voice minutes and minimum commitments often add more than the unit price.
- Price voice separately. Two of the three keep voice pricing behind sales.
- Check renewal terms. Ask about auto-renewal, annual escalators and what happens to unused committed volume.
Sources
- Decagon, "Decagon vs Sierra," https://decagon.ai/vs/sierra, checked 2026-11-12
- Sierra, "Outcome-based pricing for AI agents," https://sierra.ai/blog/outcome-based-pricing-for-ai-agents, checked 2026-11-12
- Sierra homepage (channels, customers), https://sierra.ai/, checked 2026-11-12
- Fin, "Pricing," https://fin.ai/pricing, checked 2026-11-12
- Intercom, "Pricing," https://www.intercom.com/pricing, checked 2026-11-12
- eesel AI, "Decagon AI pricing in 2026" (cites Vendr data; competitor-authored), https://www.eesel.ai/blog/decagon-ai-pricing, checked 2026-11-12
- Featurebase, "Sierra AI Pricing 2026" (cites SelectHub; competitor-authored), https://www.featurebase.app/blog/sierra-ai-pricing, checked 2026-11-12
- Open, "Pricing," https://www.open.cx/pricing, checked 2026-11-12
- Open, "FareHarbor customer story," https://www.open.cx/customer-stories/fareharbor, checked 2026-11-12