MineBench: Fable 5.1 costs 2.7x more than Fable 5 on identical builds despite unchanged API prices
r/ClaudeAI and r/singularity (539 and 154 upvotes), MineBench·high signal
A MineBench run of 15 Minecraft builds put Fable 5.1 at $147.55 total against Fable 5's $54.93, with average inference time rising from 18m 04s to 40m 12s. Output size barely moved (34.07 MiB average versus 30.65 MiB, largest 88.76 MiB), so the operator attributes the gap to substantially longer reasoning rather than more output. Anthropic advertises identical per-token API pricing for both models, which means anyone budgeting an agent loop off list prices will be roughly 3x under on 5.1.