{"i":20,"slug":"prompt-cache-break-even","chart":{"id":"cache-break-even-cost-curve","title":"Cost of a reused prefix with and without the cache, by session length (calculation)","subtitle":"Prefix of 7,831 tokens (Sonnet 5.5) and 7,828 tokens (Opus 5.5), the rounded mean turn-1 input; n = 3 Sonnet sessions (range 7,831 to 7,832) and 3 Opus sessions (the same in every session); USD per 1,000 sessions","kind":"line","unit":"usd","xLabel":"Turns in the session (requests that send the prefix)","yLabel":"USD per 1,000 sessions (list price)","series":{"$k":["name","points"],"$r":[["Claude Sonnet 5.5 (no cache)",{"$k":["label","value"],"$r":[["1 turn",15.66],["2 turns",31.32],["3 turns",46.99],["5 turns",78.31],["10 turns",156.62],["20 turns",313.24]]}],["Claude Sonnet 5.5 (1-hour cache write)",{"$k":["label","value"],"$r":[["1 turn",31.32],["2 turns",32.89],["3 turns",34.46],["5 turns",37.59],["10 turns",45.42],["20 turns",61.08]]}],["Claude Opus 5.5 (no cache)",{"$k":["label","value"],"$r":[["1 turn",31.31],["2 turns",62.62],["3 turns",93.94],["5 turns",156.56],["10 turns",313.12],["20 turns",626.24]]}],["Claude Opus 5.5 (1-hour cache write, read $0.2 per M)",{"$k":["label","value"],"$r":[["1 turn",62.62],["2 turns",64.19],["3 turns",65.76],["5 turns",68.89],["10 turns",76.71],["20 turns",92.37]]}],["Claude Opus 5.5 (1-hour cache write, read $0.4 per M)",{"$k":["label","value"],"$r":[["1 turn",62.62],["2 turns",65.76],["3 turns",68.89],["5 turns",75.15],["10 turns",90.8],["20 turns",122.12]]}]]},"note":"Calculation, not a bill. The chart multiplies list prices by a prefix of 7,831 tokens (Sonnet) or 7,828 tokens (Opus). It uses a 1-hour write at 2× input and treats the whole prefix as new. It leaves out output and the tokens that each turn adds. The cache costs more at 1 to 2 turns and less from 3. The second Opus line uses a $0.4 cache read, which another table of the product lists. We did not check the vendor price. The table adds the 5-minute write.","sourceIds":["calc-cache-pricing","agent-caching-consistency","price-anthropic","price-openai"]}}