Claude Haiku vs Sonnet 5.5: 18x Cheaper and Just as Accurate in a Three-Task API Test

Description and use

Claude Haiku 5.5 and Claude Sonnet 5.5 achieved identical accuracy (15/15) on three tasks, but Haiku was 18× cheaper and faster, making it suitable for high‑volume office workflows.

Problem

Choosing a cost‑effective LLM for short office tasks while maintaining accuracy.

Outcome

Haiku 5.5 achieved identical accuracy to Sonnet 5.5 on three tasks, completed 18× faster and at 18× lower cost, demonstrating its suitability for high‑volume, latency‑sensitive office workflows.

Workflow

• Define three office tasks with hand‑verified answers
• Send identical prompts to Haiku and Sonnet via Claude API
• Record response time, token counts, and cost
• Grade each task with code: 5 invoice fields, 6 commission figures, 4 email conditions
• Compare accuracy, speed, and cost

Evidence

Both scored 15/15 on code‑graded checks.

Source

Haiku also finished faster (11.7 s vs 15.7 s in total) and cost 18 times less ($0.00129 vs $0.02357).

Source

On the price list, Claude Haiku 5.5 costs a twentieth of Claude Sonnet 5.5.

Source