Flex and Batch Cost the Same but Aren't Identical

The mistake

Assuming Flex and Batch are two names for the same thing because they're priced identically for every text model that offers both — and then picking whichever one happens to be top of mind, expecting the same guarantee from either.

Why this happens

The pricing tables really are numerically identical, published as two separate tables that happen to match, row for row, for every model this site tracks. It's a reasonable inference from "same price" to "same product," and OpenAI's own naming doesn't do much to head that inference off — nothing in either name signals which one carries a stronger delivery commitment.

Why it matters

The two differ specifically on the completion guarantee, not on cost, and that's exactly the axis that matters if a job has any deadline sensitivity at all. Batch commits to a fixed completion window. Flex doesn't carry that same guarantee. A job picked into Flex under the assumption that "it's the same as Batch, just a different name" can complete later than a Batch job with identical token counts would have — not because anything went wrong, but because Flex was never promising the same thing in the first place.

The fix

Choose between the two based on whether your job needs the fixed-window guarantee, not based on price — since price gives you no signal either way. A job with a real deadline that fits inside Batch's published window belongs on Batch specifically for that guarantee. A job that's price-sensitive and delay-tolerant but doesn't need a hard deadline commitment is a reasonable fit for Flex. Treating the choice as arbitrary because the prices match is the one framing that's actually wrong here.

It's worth asking, the next time a job's tier assignment comes up for review, whether it was chosen deliberately for its guarantee or just inherited from whichever tier someone picked first — because with the prices identical, there's no cost signal that would ever surface a wrong pick on its own.

See also

Service Tiers: Standard, Batch, Flex & Fast lays out what genuinely differs between all four tiers, not just the two that happen to share a price.