AssemblyAI vs OpenAI: Token Pricing, Speed & Intelligence
Full comparison of AssemblyAI and OpenAI — live token pricing, latency, throughput, context window, strengths, weaknesses, and best use cases. Rates sourced from public APIs — verify before use.
AssemblyAI
Universal-2 speech-to-text with speaker diarisation and audio intelligence
AssemblyAI provides a speech-to-text and audio intelligence API. Its Universal-2 model offers high-accuracy transcription with built-in speaker diarisation, sentiment analysis, topic detection, and PII redaction. The Nano model targets cost-sensitive batch workloads. Pricing is per audio hour.
OpenAI
GPT-6 Astra, GPT-5.6 Sol/Terra/Luna — plus image, voice, and realtime APIs
OpenAI's September 2026 API lineup spans GPT-6 Astra (flagship frontier), GPT-5.6 Sol (promotional), GPT-5.6 Terra (balanced), and GPT-5.6 Luna (everyday). Beyond text, the platform includes GPT-Image-2.5 (Sunburst and Flare), GPT-Live-1 voice, GPT-Realtime-2.1 for low-latency voice agents, and transcription/translation models. Batch API saves 50% on all models. Check the live table for current per-token rates.
Key metric comparison
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Live token pricing
Strengths and weaknesses
AssemblyAI
OpenAI
Key differentiators
Universal-2 bundles transcription with speaker diarisation, sentiment, topic detection, and PII redaction — plus LeMUR for LLM-powered audio Q&A — in a single API call.
A broad AI API platform — GPT-6 Astra to GPT-5.6 Luna covering multiple capability tiers, plus native image, voice, realtime, and transcription APIs under one key.
Frequently asked questions
AssemblyAI FAQs
How is AssemblyAI priced?
AssemblyAI charges per audio hour. Universal-2 is $0.37/hour and Nano is $0.10/hour. Additional audio intelligence features (diarisation, sentiment, PII redaction) are priced separately. See assemblyai.com/pricing for current rates.
What is Universal-2?
Universal-2 is AssemblyAI's flagship transcription model with built-in speaker diarisation, sentiment analysis, topic detection, and PII redaction. It is designed for meeting intelligence and call analytics use cases.
What is LeMUR?
LeMUR (Leveraging Large Language Models to Understand Recorded Audio) is an AssemblyAI feature that lets you run LLM-powered Q&A, summarisation, and action-item extraction directly over transcribed audio without building a separate pipeline.
OpenAI FAQs
What are the latest OpenAI models as of 2026?
OpenAI's current lineup includes GPT-6 Astra (flagship frontier), GPT-5.6 Sol (promotional), GPT-5.6 Terra (balanced), and GPT-5.6 Luna (everyday). The o-series reasoning models remain available for complex multi-step tasks. Check the live table or platform.openai.com/docs/pricing for current rates.
How much does the OpenAI API cost?
OpenAI uses tiered per-token pricing across its model lineup. The Batch API cuts all prices by 50% for async workloads, and prompt caching reduces input costs by 50% on eligible requests. Check platform.openai.com/docs/pricing for current rates.
Does OpenAI support prompt caching?
Yes. Prompt caching is available on GPT-6 Astra, GPT-5.6 Sol, and other major models. Cached input tokens are billed at 50% of the standard input price, making long-context and repeated-system-prompt workloads significantly cheaper.
Provider resources
AssemblyAI — Universal-2 speech-to-text with speaker diarisation and audio intelligence
AssemblyAI provides a speech-to-text and audio intelligence API. Its Universal-2 model offers high-accuracy transcription with built-in speaker diarisation, sentiment analysis, topic detection, and PII redaction. The Nano model targets cost-sensitive batch workloads. Pricing is per audio hour.
Universal-2 bundles transcription with speaker diarisation, sentiment, topic detection, and PII redaction — plus LeMUR for LLM-powered audio Q&A — in a single API call.
OpenAI — GPT-6 Astra, GPT-5.6 Sol/Terra/Luna — plus image, voice, and realtime APIs
OpenAI's September 2026 API lineup spans GPT-6 Astra (flagship frontier), GPT-5.6 Sol (promotional), GPT-5.6 Terra (balanced), and GPT-5.6 Luna (everyday). Beyond text, the platform includes GPT-Image-2.5 (Sunburst and Flare), GPT-Live-1 voice, GPT-Realtime-2.1 for low-latency voice agents, and transcription/translation models. Batch API saves 50% on all models. Check the live table for current per-token rates.
A broad AI API platform — GPT-6 Astra to GPT-5.6 Luna covering multiple capability tiers, plus native image, voice, realtime, and transcription APIs under one key.
Key strengths compared
AssemblyAI
- Universal-2 includes speaker diarisation, sentiment, topics, and PII redaction out of the box
- Audio intelligence features reduce need for post-processing pipelines
- Nano tier at $0.10/hour for cost-sensitive batch transcription
- Speech and audio only — no general-purpose LLM or image models
- Per-hour pricing model differs from token-based LLM APIs
OpenAI
- Wide API surface: text, image, voice, realtime, transcription, translation, web search, code execution
- GPT-6 Astra at the frontier; GPT-5.6 Sol at promotional pricing
- Prompt caching on all major models (10% of input price)
- No open-weight models — full vendor lock-in
- GPT-6 Astra output pricing is among the highest for frontier tier — check live table
Key weaknesses compared
AssemblyAI
- Speech and audio only — no general-purpose LLM or image models
- Per-hour pricing model differs from token-based LLM APIs
- Advanced audio intelligence features add cost on top of base transcription
OpenAI
- No open-weight models — full vendor lock-in
- GPT-6 Astra output pricing is among the highest for frontier tier — check live table
- Rate limits can be restrictive on lower tiers
Provider category context
AssemblyAI is a frontier lab, founded in 2017. OpenAI is a frontier lab, founded in 2015. Both are frontier lab providers — the comparison is primarily about pricing, model selection, and feature differentiation within the same tier.
How to choose between them
Both AssemblyAI and OpenAI are frontier labs with proprietary models. Choose based on benchmark performance for your specific task: AssemblyAI leads on universal-2 includes speaker diarisation, sentiment, topics, and pii redaction out of the box, while OpenAI leads on wide api surface: text, image, voice, realtime, transcription, translation, web search, code execution. For cost-sensitive workloads, compare the cheapest model tier from each provider in the pricing table above — the gap between efficient-tier models is often larger than between flagship models.