Grok offers a Basic plan at $15/month allowing up to 10 prompts every 2 hours,...

https://telegra.ph/How-Much-Does-Realtime-Voice-Cost-on-the-Grok-API-10-14

Grok offers a Basic plan at $15/month allowing up to 10 prompts every 2 hours, and a Pro plan at $40/month with the same prompt cap but faster response times. Both paid plans do not include a free trial