Calculate the complete per-minute and monthly unit economics of full-duplex conversational voice agents: Itemize Speech-to-Text (STT), LLM reasoning, Text-to-Speech (TTS), and SIP telephony across Deepgram, Groq, Cartesia, ElevenLabs, OpenAI, and Twilio.
⚡ 60-Second Voice Telephony Verdict✓ Verified October 2026
Full Stack STT + LLM + TTS + SIP Unit Economics
Voice AI Cost Verdict: Production Voice AI bots cost $0.05 to $0.11 per call minute: Deepgram Nova-2 STT ($0.0043/min), Groq Llama-3.3 LLM ($0.012/min), Cartesia Sonic TTS ($0.032/min), and Twilio SIP telephony ($0.014/min). Sub-500ms voice pipeline benchmarks are detailed in our Voice & Speech Hub and Cartesia vs Deepgram Aura.
All-in Minute Cost$0.05 – $0.11 / Min
Deepgram Nova-2$0.0043 / Minute
Cartesia Sonic TTS$0.032 / Minute
Twilio Carrier SIP$0.014 / Minute Inbound
Executive Verdict & Voice Unit Economics
A production real-time conversational voice AI agent costs between $0.055 and $0.075 per minute when built with a sub-600ms ultra-low latency stack (Deepgram Nova-2 + Groq Llama 3.3 70B + Cartesia Sonic + Telnyx SIP). Switching to premium components (ElevenLabs Flash v2 + GPT-4o + Twilio SIP) increases costs by 3x to $0.18 - $0.22 per minute. Telephony transport (Twilio at $0.014/min) and TTS audio generation ($0.04 - $0.08/min) represent over 75% of the total bill, while the LLM reasoning layer accounts for less than 10%.
Optimized Stack Cost$0.062 / minute
Premium Stack Cost$0.185 / minute
Turn-Taking Latency450ms - 650ms
TTS Cost Share55% - 70% of Bill
Voice AI Agent Stack Components & Unit Rates (2026)
Breakdown of unit rates across the four mandatory layers of real-time full-duplex voice pipelines.
Layer / Component
Leading Provider / Option
Unit Pricing Formula
P50 Turn-Taking Latency Contribution
1. Speech-to-Text (STT)
Deepgram Nova-2 Streaming
$0.0059 / audio minuteSpeed Leader
~180ms - 240ms (Endpointing included)
2. Brain / LLM Reasoning
Groq LPU (Llama 3.3 70B)
$0.59 / 1M in • $0.79 / 1M out
~120ms - 180ms TTFT (280 tokens/sec)
3. Text-to-Speech (TTS)
Cartesia Sonic (Fast WebSockets)
$0.075 / 1,000 characters (~$0.045/min)
~90ms - 130ms TTFB audio generation
4. Telephony / SIP Transport
Telnyx SIP Trunking
$0.0050 / phone minute
~40ms - 80ms VoIP transcoding
Alternative: Premium TTS
ElevenLabs Flash v2
$0.150 / 1,000 characters (~$0.090/min)
~150ms - 220ms TTFB
Alternative: Premium Telco
Twilio Voice SIP + Media Streams
$0.0140 / min + $0.0040 / min media stream
~60ms - 100ms
Interactive Voice AI Agent Cost Simulator
Calculate your itemized per-minute and monthly invoice based on call volume, duration, and chosen component stack.
500 calls25,000 calls50,000 calls
1 minute7.5 minutes15 minutes
Itemized Cost Breakdown (35,000 Total Minutes)
1. STT (Deepgram Nova-2 Streaming):$206.50
2. LLM Reasoning (Groq Llama 3.3):$52.50
3. TTS Synthesis (Cartesia Sonic):$1,575.00
4. Telephony SIP (Telnyx Voice):$175.00
Total Monthly Invoice:$2,009.00
Blended Cost Per Call Minute
$0.057 / min
Full-duplex turn-taking latency: ~520ms P50.
Production Code Implementations
Explore how to wire a full-duplex voice pipeline with sub-600ms latency using Pipecat and LiveKit.
// ============================================================// 1. LIVEKIT AGENTS: Ultra-Low Latency Voice Dispatcher// Pipeline: Deepgram STT -> Groq LLM -> Cartesia TTS// ============================================================import { JobContext, WorkerOptions, cli } from"@livekit/agents";
import * as deepgram from"@livekit/agents-plugin-deepgram";
import * as cartesia from"@livekit/agents-plugin-cartesia";
import * as openai from"@livekit/agents-plugin-openai";
export defaultasyncfunctionentrypoint(ctx: JobContext) {
await ctx.connect();
const voicePipeline = new VoicePipelineAgent({
stt: new deepgram.STT({ model: "nova-2" }),
llm: new openai.LLM({
baseURL: "https://api.groq.com/openai/v1",
model: "llama-3.3-70b-versatile",
apiKey: process.env.GROQ_API_KEY
}),
tts: new cartesia.TTS({ voice: "248be419-c632-4f23-afd1-534b0c73d945" }),
interruptible: true// Automatically cancels TTS on human barge-in
});
voicePipeline.start(ctx.room);
}
# ============================================================# 2. PYTHON: Pipecat Full-Duplex Pipeline (Daily.co WebRTC)# ============================================================import os
from pipecat.pipeline.pipeline import Pipeline
from pipecat.services.deepgram import DeepgramSTTService
from pipecat.services.cartesia import CartesiaTTSService
from pipecat.services.groq import GroqLLMService
stt = DeepgramSTTService(api_key=os.getenv("DEEPGRAM_API_KEY"))
llm = GroqLLMService(api_key=os.getenv("GROQ_API_KEY"), model="llama-3.3-70b-versatile")
tts = CartesiaTTSService(api_key=os.getenv("CARTESIA_API_KEY"), voice_id="sonic-english")
# Assemble streaming pipeline with automatic interruption cancellation
pipeline = Pipeline([stt, llm, tts])
Real-World Production Scenarios & Itemized Bills
Explore 3 enterprise workloads detailing how architectural decisions impact customer experience and monthly bills.
Scenario A: Dental Clinic AI Receptionist (Inbound)
5,000 inbound patient calls/month • 3.0 min avg duration • 15,000 mins
An automated front-desk agent scheduling appointments, confirming insurance coverage, and answering hours of operation.
25,000 outbound lead calls/month • 2.0 min avg • 50,000 mins
A mortgage brokerage qualifying refinance leads in real time. 80% of calls end in under 45 seconds if the lead is unqualified.
Deepgram + Groq + Cartesia + Twilio SIP:
50,000 mins STT ($0.0059/min)$295.00
LLM Tokens (Groq 70B)$75.00
Cartesia TTS (With Barge-in Caching)$1,650.00
Twilio SIP Outbound ($0.014/min)$700.00
Total Bill ($0.054 / min):$2,720.00 / mo
Switching Twilio to Telnyx:
Telnyx SIP Outbound ($0.005/min)$250.00
Telephony Savings-$450.00
New Total ($0.045 / min):$2,270.00 / mo
Verdict: Switching SIP saves $450/month. At 50k minutes, migrating from Twilio to Telnyx reduces telephony bills by 64% with zero audio quality impact.
2,000 VIP member calls/month • 8.0 min avg • 16,000 mins
A luxury hospitality service where voice realism, subtle breathing, and emotional inflection must be completely indistinguishable from human concierges.
Premium Expressive Stack (ElevenLabs + GPT-4o):
16k mins STT (Deepgram Nova-2)$94.40
GPT-4o Reasoning (Complex itineraries)$480.00
ElevenLabs Flash v2 ($0.15/1k chars)$1,728.00
Twilio High-Def SIP Trunk$288.00
Total Bill ($0.162 / min):$2,590.40 / mo
Verdict: $0.16/min is justified for VIP luxury. For high-ticket services where human-level inflection drives bookings, paying for ElevenLabs and GPT-4o generates massive ROI.
Architectural Deep-Dive: The 600ms Latency Budget
How every millisecond is accounted for in real-time conversational voice architectures.
1. The Breakdown of Latency Steps
In natural face-to-face dialogue, humans respond in 200 to 400 milliseconds. On telephone networks, delays exceeding 700ms cause both parties to talk over each other in awkward collisions. A well-engineered Voice AI pipeline allocates its latency budget as follows:
Audio Buffering & VAD (Voice Activity Detection): 100ms - 150ms to detect that the caller has finished their sentence.
Streaming STT Transcription (Deepgram Nova-2): 80ms - 120ms to emit the final transcript.
LLM Time-to-First-Token (Groq LPU): 120ms - 180ms to stream the first words of the answer.
Streaming TTS Time-to-First-Byte (Cartesia Sonic): 90ms - 120ms to convert the initial text chunk into raw PCM audio bytes.
Total Turn-Taking Latency: ~440ms to 650ms (Imperceptible conversational delay).
2. Interruption Handling (Barge-In)
Without barge-in, if a caller interrupts the bot ("Wait, I meant Tuesday, not Wednesday!"), the bot will continue reading its 15-second response blindly. A modern orchestrator (such as LiveKit or Pipecat) runs continuous Voice Activity Detection on the inbound audio track.
The instant human speech energy is detected, the server sends a CLEAR_BUFFER command to the client's audio sink and cancels the active LLM generation stream. This immediately frees up server resources and avoids paying for wasted TTS audio generation.
Production Voice AI Checklist
Essential engineering practices before launching telephone voice agents to production users.
✓
1. Enforce Streaming WebSockets End-to-End:
Never use REST polling endpoints for audio. All three core layers (Deepgram STT, Groq LLM, and Cartesia TTS) must communicate via bidirectional WebSocket streams.
✓
2. Implement Barge-In Cancellation:
Ensure your client terminates outgoing TTS playback within 80ms of human speech detection. This prevents caller frustration and cuts TTS billing by 20%.
✓
3. Evaluate Wholesale SIP Trunking:
If your call volume exceeds 10,000 minutes per month, migrate away from standard Twilio Voice rates ($0.014/min) to Telnyx ($0.005/min) or a private FreeSWITCH SBC.
✓
4. Instruct the LLM to Generate Short Conversational Turns:
Add a system prompt directive: "Speak in 1-2 concise sentences. Do not use markdown bullet points or long monologues." This keeps turn latency low and keeps TTS bills minimal.
Frequently Asked Questions
What is the typical per-minute cost of a real-time conversational voice AI agent?
In 2026, an optimized production voice AI stack (Deepgram Nova-2 STT + Groq Llama 3.3 70B LLM + Cartesia Sonic TTS + Telnyx SIP) costs approximately $0.055 to $0.075 per conversational minute. Using premium components (such as ElevenLabs Flash v2 + OpenAI GPT-4o + Twilio SIP) raises the cost to $0.16 to $0.22 per minute.
What is the total latency budget for human-like conversational turn-taking?
Natural human conversation requires responses within 500 to 700 milliseconds. A production Voice AI latency budget allocates: ~200ms for Speech-to-Text endpointing (Deepgram Nova-2), ~150ms for LLM Time-to-First-Token (Groq Llama 3.3), ~100ms for Text-to-Speech Time-to-First-Byte (Cartesia Sonic), and ~100ms for WebSocket network transport and SIP transcoding.
Why is Groq Llama 3.3 preferred over OpenAI GPT-4o for voice agents?
Groq LPUs deliver an ultra-fast Time-to-First-Token of under 180 milliseconds at 250+ tokens/sec, preventing conversational dead air. Furthermore, Groq Llama 3.3 70B costs only $0.59/1M input and $0.79/1M output, making the LLM reasoning layer virtually free (<$0.003/min) compared to GPT-4o ($2.50/$10.00).
How does telephony transport impact the voice agent bill?
Telephony transport represents a major hidden cost. Twilio charges $0.014 per minute for inbound/outbound calls, plus $0.004/min for media streaming WebSockets. Switching to wholesale SIP providers like Telnyx ($0.005/min) or hosting on-premise Asterisk/FreeSWITCH servers can reduce telephony costs by 65%.
How is Text-to-Speech (TTS) billed during phone calls?
TTS providers bill based on generated character counts. An average voice bot speaks approximately 120 to 150 words per minute (~600 to 750 characters). On Cartesia Sonic ($0.075 per 1,000 characters), this costs ~$0.045 to $0.055 per conversational minute. On ElevenLabs ($0.15/1k chars), TTS costs ~$0.09 to $0.11 per minute.
What is barge-in / interruption handling, and how does it affect costs?
Barge-in allows human callers to interrupt the AI mid-sentence. When interruption is detected, the orchestrator immediately cancels the streaming TTS audio buffer and aborts LLM token generation. Proper interruption handling saves up to 25% on TTS and LLM token billing by cutting off unneeded synthesized speech.