xAI Grok Speech APIs Review: STT at $0.10/hr, TTS at $4.20/M Chars, Battle-Tested on Tesla and Starlink

xAI launched standalone Grok Speech-to-Text and Text-to-Speech APIs on April 18, 2026. STT prices at $0.10/hr batch and $0.20/hr streaming — below ElevenLabs, Deepgram, and AssemblyAI — and claims 5.0% error on phone call entity recognition vs. 12–21% for rivals. TTS delivers five voices across 20 languages at $4.20/M characters. We review the specs, pricing, and what this means for the voice developer market.