Skip to content
AI Receptionist Report

Head-to-head

Synthflow vs Retell

Enterprise voice-agent platform with contracts from $30,000 a year versus a pay-as-you-go developer platform from $0.07 a minute: vendor-built or self-built?

By Network Editorial Team

Last updated

Disclosure: This website may receive compensation from companies mentioned on this page. The publisher may also have an ownership or financial relationship with certain featured providers. These relationships do not change our stated evaluation methodology. The publisher of this website has a financial interest in Torklio. Read the full disclosure.

SF

Synthflow

Larger teams that want custom call flows built with vendor support

Enterprise voice-agent platform; contracts start at $30,000 per year.

Starting price: Pricing verification needed

Read the Synthflow review
RT

Retell AI

Developers building a custom voice agent

Developer voice-agent platform, pay-as-you-go from about $0.07 to $0.31 per minute.

Starting price: $0/mo

Read the Retell AI review

Decision summary

This comparison changed when we checked the pricing pages on September 7, 2026. Synthflow's page now lists enterprise contracts only, starting at $30,000 a year and scoped to volume, concurrency, telephony and integrations, with implementation, security review and an SLA included and no monthly plan or trial. Retell remains pay-as-you-go with no monthly fee, $10 in free credits and a published all-in rate of $0.07 to $0.31 a minute, but your engineers build everything. Choose Synthflow if you are a larger organization that wants a custom agent delivered and supported under contract and can commit five figures a year. Choose Retell if you have developers and want to start for the price of a coffee. A small business without engineers should choose neither and look at a packaged product instead.

Feature differences

Build method

Synthflow
Vendor-scoped agent with implementation, onboarding, training and launch support in the contract (verified).
Retell AI
Code against APIs and SDKs; your team builds.

Depth of control

Synthflow
Custom concurrency, routing, escalation and fallback logic per contract (verified).
Retell AI
Deeper; every prompt and function is yours.

Outbound calls

Synthflow
Yes (unverified).
Retell AI
Yes (unverified).

Integrations

Synthflow
CRM, calendar, contact-center, webhook, API and knowledge-source integrations listed in contract scope; no systems named.
Retell AI
Custom functions; you write the connectors.

Human backup

Synthflow
None; escalation paths are built into the contract scope.
Retell AI
None; transfers must be built.

Appointment scheduling

Synthflow
Calendar integrations within contract scope (verified); mechanics not independently verified.
Retell AI
Partial; requires a custom function or tool integration (not independently verified).

Telephony

Synthflow
Native telephony or SIP trunking into an existing phone system (verified).
Retell AI
Packaged telephony at $0.015 per minute and $2 per number (verified).

Security and compliance

Synthflow
MSA, DPA and security review in the contract (verified).
Retell AI
PII removal add-on at $0.01 per minute (verified); enterprise terms custom.

Call recording and transcripts

Synthflow
Not stated on the pricing page; confirm with the vendor.
Retell AI
Recorded as available (not independently verified).

Setup responsibility

Synthflow
The vendor implements to an agreed scope; your team owns requirements and review.
Retell AI
Developers or an agency write the agent; nothing works until the code exists.

Ongoing maintenance

Synthflow
Enterprise SLA and support; flow changes go through the vendor or your admins.
Retell AI
Code changes, testing and releases, done by the engineering team.

Pricing differences

Entry price

Synthflow
Enterprise contracts start at $30,000 annually; no monthly plan published.
Retell AI
$0 monthly; pay-as-you-go.

What the meter is

Synthflow
Scoped per contract: call volume, concurrency, telephony and integrations.
Retell AI
Per minute: $0.055 voice infrastructure plus LLM, text-to-speech and telephony.

Published per-minute cost

Synthflow
Not published.
Retell AI
$0.07 to $0.31 all-in.

Trial or free usage

Synthflow
None listed.
Retell AI
$10 in free credits at signup.

Contract term

Synthflow
Annual contracts only.
Retell AI
No contract; Enterprise plan offers custom volume pricing.

Use-case differences

Operations team without engineers

Synthflow
Fit only at enterprise scale; the vendor does the building, but the contract starts at $30,000 a year.
Retell AI
Not viable.

Software product embedding voice

Synthflow
Possible under contract, but the scope model suits an internal deployment better.
Retell AI
Strong fit.

Small general contractor with an office manager

Synthflow
Not a fit at this price; see Frontdesk, Rosie Scale or Dialzara for under $150 a month.
Retell AI
Only viable if the contractor retains a developer, which is rare at that size.

Regional roofing or HVAC company with several branches

Synthflow
Plausible: custom routing per branch, SIP into an existing phone system and vendor-led launch; see [roofing](/industries/roofing).
Retell AI
Plausible with an agency; the campaign and routing logic is code.

Agency delivering agents to many clients

Synthflow
The contract model does not suit per-client resale.
Retell AI
Strong fit: per-minute pricing and 20 free concurrent calls scale across clients.

Pros and cons

Synthflow

Pros

  • Vendor-led implementation and launch support
  • Enterprise SLA, security review, SIP options
  • Broad integration scope

Cons

  • $30,000 a year minimum
  • No monthly plan or trial
  • Not self-serve

Retell AI

Pros

  • No monthly fee; $0.07–$0.31 a minute
  • $10 free credits to start
  • Full control

Cons

  • Engineers required
  • Maintenance burden
  • No implementation help

Which one should you choose?

Choose Synthflow if…

  • You are a larger organization with a five-figure annual budget for phone automation.
  • You want the vendor to implement, train and support the agent under an SLA.
  • You need SIP trunking, a security review and an MSA before anything goes live.

Choose Retell AI if…

  • You have developers and a product roadmap.
  • You want to start today for the cost of the minutes you use.
  • The agent is part of a product you sell, not a back-office tool.

Side by side

SF
Synthflow

Larger teams that want custom call flows built with vendor support

Starting price
Pricing verification needed
24/7 answering
Yes†
Appointment scheduling
Yes
Call transfers
Yes
Human backup
No
CRM integration
Yes
Developer access (API)
Yes
Industry specialization
No†
Test score
Sample only
Review status
Editorial Preview
RT
Retell AI

Developers building a custom voice agent

Starting price
$0/mo
24/7 answering
Yes†
Appointment scheduling
Partial†
Call transfers
Yes†
Human backup
No
CRM integration
Partial†
Developer access (API)
Yes
Industry specialization
No†
Test score
Sample only
Review status
Editorial Preview

† Not independently verified: based on the provider's public materials or editorial knowledge, not yet checked against a dated source. “Verify” means no data has been entered yet. Test scores appear only when the 10-call challenge has been completed for that provider.

How we compared them

Both pricing pages were checked on September 7, 2026. Synthflow's page lists a single enterprise offering with contracts from $30,000 a year, itemizing what a contract scopes: volume, concurrency, telephony, integrations, security review and launch support. The self-serve no-code tiers it was once known for were not visible. Retell's page publishes component rates and an all-in range. The feature rows come from each vendor's public materials, and neither has been through the lab.

The workflow after the call

In a Synthflow engagement the post-call workflow is specified and built to scope: the agent captures the caller's answers, integrations write them to a CRM or calendar, and escalation and fallback rules decide what happens when the agent is stuck, with the vendor implementing and supporting the result. In Retell the same workflow is coded by your team: the agent invokes a function you wrote, that function talks to your systems, and the results feed back into the conversation. Neither platform supplies a ready-made qualification model, customer history or calendar conflict check, so the quality of what happens after the call is the quality of the scope you agreed or the code you wrote.

Total cost of ownership considerations

The two are now priced for different buyers. Synthflow's $30,000 annual floor is a budget line, and it buys implementation, onboarding, training, an SLA and a security review that Retell leaves to you. Retell's cost is usage: at the published $0.07 to $0.31 a minute, 10,000 minutes a month runs $700 to $3,100, with 20 concurrent calls included and $8 a month for each beyond. The dominant cost on Retell is people: a developer's or an agency's hours to build and maintain the agent. A rough way to think about it is that Synthflow has priced that labor into the contract, and Retell has not. For an organization with engineers, Retell is far cheaper; for one without them and with enterprise-scale volume, Synthflow's contract may cost less than hiring.

What would change this verdict

  • Synthflow restoring a self-serve monthly plan would reopen it as a small-business no-code option and change this page substantially.
  • A lab build of the same agent on each platform would tell us whether vendor implementation produces a better receptionist than a developer build.
  • Confirmation of Synthflow's recording and transcript capability would turn that row from a Retell edge into a tie.
  • Retell shipping a maintained no-code layer would make it viable for operations teams without engineers.

Neither vendor here is affiliated with the publisher of AI Receptionist Report, which does have a financial interest in Torklio, a packaged product that owners without an enterprise budget or a developer should consider instead.

Frequently asked questions

Is Synthflow easier than Retell?

Under its enterprise model the vendor does the building, so yes, but only for organizations that can commit to a contract starting at $30,000 a year (verified September 7, 2026).

Which is cheaper?

Retell, by a very wide margin at small and medium volume: no monthly fee and $0.07 to $0.31 a minute against Synthflow's $30,000 annual minimum. Synthflow's price includes implementation and support that Retell does not.

Do either replace a packaged receptionist?

Only if you build or commission one. Business owners should compare Torklio, Goodcall, Rosie, Dialzara or Frontdesk instead.

Can I start in Synthflow and migrate to Retell later?

The agent logic would be rewritten as code, so plan on a rebuild rather than an export. Choose the platform whose operator, and whose budget, you will actually have in a year.

Which handles booking better out of the box?

Neither books appointments natively. Synthflow reaches calendars through integrations scoped in the contract; Retell requires a custom function. Neither includes the conflict checks that a packaged product like Torklio verifies.

Sources

  1. Synthflow pricing (accessed 2026-09-07)
  2. Retell AI pricing (accessed 2026-09-07)