The closest alternative to Mercury 2 is Claude Sonnet 4 — comparable intelligence (33.0 vs 32.8); for a cheaper option, MiMo-V2.5 runs $0.140/M vs $0.250/M; for more speed, gpt-oss-120b (free) hits 554 t/s; and the best open-weight substitute is MiniMax M3.
Claude Sonnet 4 is the closest alternative to Mercury 2, with an Intelligence Index of 33.0 (Mercury 2 scores 32.8) at $3.00 per million input tokens.
Yes — MiMo-V2.5 costs $0.140 per million input tokens versus $0.250 for Mercury 2, while staying within ~8 points of its Intelligence Index.
MiniMax M3 is the strongest open-weight alternative to Mercury 2 — downloadable from Hugging Face and self-hostable, scoring 54.7 on intelligence.