Realtime voice API cost per hour: Grok, GPT-Live-1, Gemini Live

A realtime voice session costs roughly $1.38 to $4.80 per hour of continuous audio, depending on the vendor, based on the per-minute rates each vendor lists today. Sume does not run live sessions, so it is not a like-for-like replacement. If your product can tolerate a few seconds per turn, the same hour built from Sume's async speech-to-text and text-to-speech jobs comes to about $3.17 under the assumptions below.

Vendor rates, read 1 October 2026

Each row is the vendor's published rate, converted to an hourly figure by multiplying by 60. A session that is idle or only half talking costs less where the vendor bills by audio duration.

The Sume pipeline, with the arithmetic

Sume prices are listed on the API pricing page: speech-to-text is $0.01 per audio minute and text-to-speech is $0.0475 per 1,000 characters. To compare an hour, assume the user speaks for 60 minutes and the agent speaks for 60 minutes at about 150 words per minute and 6 characters per word including spaces. That is 54,000 characters of speech, which is an assumption, not a measurement.

Limits that matter more than price

The two shapes behave differently, and cost is rarely the deciding factor.

• Sume's speech-to-text takes a public HTTPS audio URL and handles up to 10 minutes per request, so you transcribe finished clips, not an open microphone stream.
• Text-to-speech is a job: submit, wait for the job, fetch the result. See jobs and results.
• Sume does not bundle a language model, so the reply text has to come from your own step. Realtime models include that reasoning in the per-minute price; the Sume total above does not.
• Vendor rates change. Recheck the three pages before you budget.

When Sume fits

Use async jobs for narration, voicemail summaries, recorded call review and voice notes, where a turn can take seconds. Use a realtime session when someone is waiting on the line. Related reading: realtime model versus async narration and which Sume audio endpoint to call.