xAI's newest Grok takes half the context of its March model and charges 140% more for output

There is a habit in this industry of reading a version number as a promise: the higher it is, the more the model does for the money. xAI's own price list breaks that habit. Grok 4.20 went live in March 2026 with a context window of one million tokens, priced at $1.25 per million input tokens and $2.50 per million output. Grok 4.3, which followed at the end of April, kept both numbers. Then the line turned. Grok 4.5 in July and Grok 4.6 in August each take 500,000 tokens - half of what their predecessors take - and are billed at $2.00 input and $6.00 output. Measured against the March model, the newest flagship costs 60% more to prompt and 140% more to answer, on a context window half the size. The two-tier billing that xAI applies across the line sharpens the gap. Any request whose prompt reaches 200,000 tokens is repriced in full at double rates, so a long document sent to Grok 4.6 is charged at $12 per million output tokens, against $5 for the same document sent to Grok 4.20. There is a second, quieter difference: Grok 4.20 and 4.3 accept Batch API requests at a 20% discount, and Grok 4.6 does not accept them at all. None of this is a deprecation story. xAI has not announced a shutdown date for either spring model, and both are still listed in the company's documentation and priced there. What the price list shows is that xAI's newer models are not successors in the usual sense - they are a separate, more expensive tier that trades context for whatever the company gained elsewhere, and the older, longer-context models remain the cheaper way to buy a million tokens from xAI. For comparison, the models xAI removed from that list did leave: Grok 3 and Grok 4 are no longer in the catalogue at all, and no shutdown date was ever published for them either.