
Claude Sonnet 5 vs. Opus 4.8: The Hidden Cost of the 'Cheaper' Frontier Model (2026)
Claude Sonnet 5 looks cheap at $2/M tokens, but a hidden tokenizer tax and adaptive thinking cycles can make it costlier than Opus 4.8 for complex agentic work.
5 articles

Claude Sonnet 5 looks cheap at $2/M tokens, but a hidden tokenizer tax and adaptive thinking cycles can make it costlier than Opus 4.8 for complex agentic work.

Is Claude Opus 4.8's 2.5x price gap still worth it? We put Sonnet 5 through a full-stack building gauntlet to find where the mid-tier model wins—and where it breaks.