The closest alternative to Claude Opus 4.8 is GPT-5.4 — comparable intelligence (56.8 vs 61.4); for a cheaper option, GPT-5.4 runs $2.50/M vs $5.00/M; for more speed, Claude Opus 4.7 hits 77 t/s; and the best open-weight substitute is MiniMax M3.
GPT-5.4 is the closest alternative to Claude Opus 4.8, with an Intelligence Index of 56.8 (Claude Opus 4.8 scores 61.4) at $2.50 per million input tokens.
Yes — GPT-5.4 costs $2.50 per million input tokens versus $5.00 for Claude Opus 4.8, while staying within ~8 points of its Intelligence Index.
MiniMax M3 is the strongest open-weight alternative to Claude Opus 4.8 — downloadable from Hugging Face and self-hostable, scoring 54.7 on intelligence.