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Pricing

Aero TTS uses a simple pay-as-you-go pricing model. You are billed per character synthesized, deducted from your thinnestAI wallet balance.

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Plan Details

Every thinnestAI account gets one flat pricing plan with all features included:
Details
Free Monthly Characters10,000
Rate Limit500 requests/min
Max Characters/Request10,000
Voice LabIncluded
StreamingIncluded
WebSocketIncluded

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Per-Model Rates

Each model has its own rate per million characters:
ModelRate (per 1M chars)Best For
aero$10.00Highest quality, lowest latency
aero-mini$2.00Cost-effective batch processing
aero-nano$0.50Lightweight, minimal resources

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How Billing Works

  1. You send a synthesis request with text.
  2. Aero TTS counts the characters in your text.
  3. The cost is calculated based on the model you selected.
  4. The amount is deducted from your thinnestAI wallet balance.
  5. Audio is returned.
If your balance is insufficient, you receive a 402 Payment Required error.

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Checking Your Balance

Your wallet balance is shared with the rest of the thinnestAI platform (chat, voice calls, etc.). 
curl https://api.thinnest.ai/api/billing/balance \
  -H "Authorization: Bearer thns_sk_YOUR_KEY"

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Topping Up

Add funds to your wallet through the Billing page in the dashboard, or via API: 
curl -X POST https://api.thinnest.ai/api/billing/topup \
  -H "Authorization: Bearer thns_sk_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "amount": 10.00 }'

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Usage Tracking

Monitor your TTS spending in the dashboard under Aero TTS > Usage, or via the API: 
curl "https://api.thinnest.ai/api/tts/usage?period=month" \
  -H "Authorization: Bearer thns_sk_YOUR_KEY"
The response includes total characters, request counts, top voices, and daily breakdowns.

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Cost Estimates

ContentCharactersCost (aero)Cost (aero-nano)
Short greeting~50$0.0005$0.000025
Support response~300$0.003$0.00015
Email read-aloud~2,000$0.02$0.001
Blog post narration~5,000$0.05$0.0025
1-hour audiobook chapter~80,000$0.80$0.04
At the aero rate ($10/million characters), 1 million characters is enough for approximately 3,000-4,000 typical voice agent responses.

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Free Allowance

Every thinnestAI account gets 10,000 free characters per month (resets on the 1st of each month). This lets you test and prototype without any charges.