xAI Grok API Review: SpaceX-Owned, 555K-GPU Colossus, and the Most Aggressive Pricing at the Frontier

xAI is the AI lab Elon Musk founded in 2023, now a SpaceX subsidiary valued at $250 billion. Its Grok API is OpenAI-compatible, offers the largest context windows of any frontier model (2M tokens on Grok 4.1 Fast), live access to X (Twitter) data, and prices that undercut GPT-4o by 5–10×. We review the infrastructure, models, pricing, enterprise readiness, and whether the Musk factor is a dealbreaker.