Understanding and comparing costs of text-to-speech models for voice agents

A comparison of production text-to-speech providers for voice agents argues that TTS is typically the largest per-minute cost in the speech-to-text, language-model, and speech-synthesis stack, making consistent pricing and concurrency terms important for developers. It identifies AssemblyAI, ElevenLabs, Cartesia, Rime, and Fish as commonly used providers, and proposes normalizing their character-based prices with a rate of 600 generated characters per call minute, based on AssemblyAI’s traffic data, because agents speak only part of a conversation. Using that conversion, the post lists approximate costs of $0.009 per minute for AssemblyAI-TTS-1, $0.024 for ElevenLabs v4 Turbo, $0.0225 for Cartesia Sonic 3.6, and $0.03 each for Rime Coda and Fish Drama 3, while reporting time-to-first-audio figures ranging from 90 milliseconds for AssemblyAI to 395 milliseconds for Rime. It also highlights concurrency limits and annual spend commitments as potentially significant, less transparent costs at other providers, contrasting them with AssemblyAI’s stated unlimited concurrency and pay-as-you-go model.

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