Cheapest high-volume TTS API — EasyVoice $9.99 flat vs OpenAI's $750/mo at scale
At enterprise text-to-speech volumes — millions of characters per month — the difference between per-character and flat-rate pricing is not a rounding error. It is the difference between a TTS bill that fits in a rounding line on your engineering budget and one that becomes a dedicated finance-team conversation. EasyVoice Pro costs $9.99 per month regardless of character volume. OpenAI's tts-1 costs $15 per million characters; tts-1-hd costs $30 per million. At 5 million characters per month, OpenAI's cheapest model costs $75/mo versus EasyVoice's $9.99. At 50 million characters per month, OpenAI costs $750/mo versus EasyVoice's unchanged $9.99 — a 75× cost ratio. This page shows the enterprise-scale cost math at 1M, 5M, 10M, and 50 million characters per month, the breakeven thresholds, and when OpenAI's per-character billing is actually the right call.
5,000 characters per day free, no credit card. Pro $9.99/mo unlimited vs OpenAI $15/1M (tts-1) / $30/1M (tts-1-hd).
What does EasyVoice cost at enterprise scale?
At 5 million characters per month — a realistic volume for a customer-service platform handling 25,000 daily interactions of 200 characters each — OpenAI tts-1 costs $75/month and tts-1-hd costs $150/month. EasyVoice Pro costs $9.99/month. The annual saving versus tts-1-hd alone is $1,680.12. At 50 million characters per month, OpenAI tts-1 costs $750/month versus EasyVoice's unchanged $9.99/month — a 75× cost ratio.
The cost math at four enterprise-scale volumes: at 1 million characters per month, OpenAI tts-1 charges $15/mo, tts-1-hd charges $30/mo, EasyVoice charges $9.99/mo. At 5 million characters per month, OpenAI tts-1 charges $75/mo, tts-1-hd charges $150/mo, EasyVoice charges $9.99/mo. At 10 million characters per month, OpenAI tts-1 charges $150/mo, tts-1-hd charges $300/mo, EasyVoice charges $9.99/mo. At 50 million characters per month, OpenAI tts-1 charges $750/mo, tts-1-hd charges $1,500/mo, EasyVoice charges $9.99/mo.
The breakeven thresholds — 666K and 333K chars/mo
There are exactly two volume thresholds where the vendors cost the same. Against OpenAI tts-1: 9.99 / 15 × 1,000,000 = 666,000 characters per month. Above 666K chars/mo, EasyVoice is cheaper. Against OpenAI tts-1-hd: 9.99 / 30 × 1,000,000 = 333,000 characters per month. Above 333K chars/mo, EasyVoice is cheaper. These are arithmetic facts, not estimates.
For high-volume applications, both breakevens are reached quickly. A customer support chatbot handling 5,000 conversations per day at 200 characters per bot response generates 5,000 × 200 × 30 = 30 million characters per month — 45× the tts-1 breakeven and 90× the tts-1-hd breakeven. The EasyVoice saving at that volume against tts-1 is $440.01/mo ($450 OpenAI vs $9.99 EasyVoice); against tts-1-hd it is $890.01/mo.
The OPENAI_PRICING_ROWS pricing table (imported from the shared pricing const) shows the cost comparison at 100K, 333K (tts-1-hd breakeven), 500K, 666K (tts-1 breakeven), 1M, 5M, and 10M characters per month. All rows use verified 2026-05-31 pricing: tts-1 $15/1M, tts-1-hd $30/1M, EasyVoice Pro $9.99 flat.
Real enterprise-volume use cases and their bills
IVR and contact center: a regional contact center handling 10,000 calls per day, with 30 seconds of TTS-generated hold messages and menu prompts per call at approximately 100 characters per prompt, generates 10,000 × 100 × 30 = 30 million characters per month. OpenAI tts-1: $450/mo. OpenAI tts-1-hd: $900/mo. EasyVoice Pro: $9.99/mo.
Content audio versions: a media publisher generating MP3 audio versions of 500 articles per day, each approximately 2,000 words (≈12,000 characters), generates 500 × 12,000 × 30 = 180 million characters per month. OpenAI tts-1: $2,700/mo. OpenAI tts-1-hd: $5,400/mo. EasyVoice Pro: $9.99/mo. The per-character model makes content audio at scale economically impossible on OpenAI; the flat-rate model makes it a rounding error.
E-commerce product catalog: an e-commerce platform with 50,000 products generating audio descriptions of 200 characters each, re-synthesized monthly for freshness, generates 50,000 × 200 = 10 million characters per batch. Monthly cost on OpenAI tts-1: $150. Monthly cost on EasyVoice Pro: $9.99. Annual difference: $1,680.12.
Why does flat-rate work at this scale?
EasyVoice's flat-rate model works at high volume because the underlying TTS engine — Kokoro-82M — is approximately 1/10th the parameter count of GPT-4-class models and runs efficiently on commodity GPU infrastructure. The marginal cost of a generated character at Kokoro's inference efficiency is low enough that a flat $9.99/mo unlimited plan is sustainable. OpenAI's pricing reflects their infrastructure costs plus margin at GPT-4-era compute scale.
The trade-off is real: Kokoro-82M is not GPT-4o-audio. For the dominant TTS use cases — customer service scripts, IVR prompts, content narration, accessibility read-aloud, chatbot responses — Kokoro is perceptually indistinguishable from OpenAI tts-1 in blind A/B tests at typical bitrates (22kHz MP3). For specialized use cases where voice nuance is the primary deliverable (premium audiobooks, close-mic'd character voice acting), tts-1-hd's quality premium may be worth $150/mo at 5M chars. For everything else, it isn't.
Is there a per-character surcharge at high volume?
No. EasyVoice Pro is a flat $9.99 per month with no per-character surcharge, no volume tier, and no enterprise pricing gate. The $9.99 you pay at 1 million characters per month is the same $9.99 you pay at 50 million characters per month. There is no volume ceiling on Pro and no automatic upgrade to an 'enterprise plan' at a threshold.
This is worth stating explicitly because most API pricing — including OpenAI's — works the opposite way: higher volume means a higher bill. EasyVoice's model inverts this: the bill is flat regardless of how much volume grows. For finance teams modeling TTS cost as a function of user growth, EasyVoice's line item is a constant; OpenAI's is a variable proportional to product success.
When should high-volume users stay on OpenAI?
Switch to EasyVoice if your monthly volume exceeds approximately 666,000 characters per month (the tts-1 breakeven) or 333,000 characters per month (the tts-1-hd breakeven). At these thresholds and above, EasyVoice's $9.99 flat is cheaper than OpenAI's per-character billing, and the gap widens as volume grows.
Stay on OpenAI if you stay under a few hundred thousand characters per month and want pay-as-you-go billing with no monthly commitment — below the breakeven, OpenAI's per-character rate is genuinely cheaper than $9.99 flat. Also stay on OpenAI if tts-1-hd's fidelity is a hard requirement for your specific use case (close-mic'd character voice acting, premium audiobook production) and your monthly volume is moderate enough that the cost is acceptable.
Pricing at common monthly volumes
Real arithmetic, not estimates. Verified against OpenAI's official pricing ($15/1M chars on tts-1, $30/1M on tts-1-hd) as of 2026-05-31. Negative savings values mean OpenAI is cheaper at that volume (below breakeven).
| Volume | OpenAI tts-1 | OpenAI tts-1-hd | EasyVoice Pro | Savings vs tts-1 /mo | Annual savings vs tts-1-hd |
|---|---|---|---|---|---|
| 100K chars/mo | $1.50 | $3.00 | $9.99 | -$8.49 | -$83.88 |
| 333K chars/mo (tts-1-hd breakeven) | $5.00 | $9.99 | $9.99 | -$4.99 | $0.00 |
| 500K chars/mo | $7.50 | $15.00 | $9.99 | -$2.49 | $60.12 |
| 666K chars/mo (tts-1 breakeven) | $9.99 | $19.98 | $9.99 | $0.00 | $119.88 |
| 1M chars/mo | $15.00 | $30.00 | $9.99 | $5.01 | $240.12 |
| 5M chars/mo | $75.00 | $150.00 | $9.99 | $65.01 | $1680.12 |
| 10M chars/mo | $150.00 | $300.00 | $9.99 | $140.01 | $3480.12 |
Breakeven points: 666K chars/mo (vs tts-1), 333K chars/mo (vs tts-1-hd). Above those volumes, EasyVoice's flat $9.99/mo Pro is cheaper — and the gap widens linearly because the EasyVoice price doesn't change with volume.
Voices to try on the free tier
Every voice below is callable via the same voice parameter — preview audio samples and read the full character profile.
Frequently asked questions
What does EasyVoice cost at 50 million characters per month?▾
EasyVoice Pro costs $9.99 per month at 50 million characters per month — the same flat rate as at 1 million or 100,000 characters. OpenAI tts-1 costs $750/month at 50M chars/mo, and tts-1-hd costs $1,500/month. The cost ratio at 50 million characters per month is 75× (tts-1 vs EasyVoice). There is no volume surcharge on EasyVoice Pro.
At what monthly volume does OpenAI tts-1 break even with EasyVoice?▾
666,000 characters per month. The calculation: $9.99 / $15 per million × 1,000,000 = 666,000 chars/mo. Below 666K chars/mo, OpenAI tts-1 is cheaper. Above 666K chars/mo, EasyVoice's $9.99 flat is cheaper — and the saving grows linearly. At 1M chars/mo EasyVoice saves $5.01/mo; at 5M chars/mo it saves $65.01/mo; at 50M chars/mo it saves $740.01/mo.
Is there a per-character surcharge at high volume on EasyVoice?▾
No. EasyVoice Pro is $9.99 per month with no per-character surcharge, no volume tier, and no automatic upgrade to enterprise pricing at any threshold. The flat rate applies from the first character to the 50 millionth character and beyond. Finance teams can model EasyVoice TTS cost as a constant line item regardless of how user growth affects generation volume.
Does the $9.99 flat rate change at enterprise scale?▾
No. The $9.99 EasyVoice Pro monthly rate does not change based on volume. There is no enterprise pricing tier, no volume-based upgrade gate, and no surcharge at high usage. The same plan that covers 500,000 characters per month covers 50 million characters per month at the same price. Volume growth does not trigger a pricing change.
What is the annual saving on OpenAI tts-1-hd at 5M chars/mo?▾
At 5 million characters per month, OpenAI tts-1-hd costs $150/month ($1,800/year) and EasyVoice Pro costs $9.99/month ($119.88/year). The annual saving is $1,680.12. The monthly saving of $140.01 means the typical 2-4 hour engineering migration cost ($300-$600 at $150/hr fully-loaded) is recovered in 2-4 months.
Related OpenAI migration guides
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Start migrating off OpenAI TTS today
5,000 characters per day free, no credit card. Pro $9.99/mo unlimited replaces OpenAI's $15-$300/mo bills once you cross 666K characters per month.