A 22,022-call personal audit finds Fable 5.1 uses 31% more tokens per prompt but costs 31% less, because cached reads bill at 25%

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A developer measured Fable 5 against Fable 5.1 across 22,022 of their own API calls and found token use per call unchanged but tokens per prompt up about 31%. Priced at API list rates the direction flips: a Fable 5 prompt averaged $1.52 and a 5.1 prompt $1.05, because nearly all the extra volume is cache reads and 5.1 bills cached reads at 25% of what Fable 5 charged. The finding directly contradicts the MineBench cost result and matters because it separates two things people are conflating, raw verbosity and how subscription usage bars are debited, which the author says he still cannot measure from transcripts.