total_cost_usd returns incorrect values (~10x too high)

Bug Description

The total_cost_usd field returned in the result event of --output-format stream-json returns values approximately 10x higher than expected, particularly noticeable with Haiku model.

Steps to Reproduce

1. Run a Claude Code command with Haiku model using --output-format stream-json
2. Parse the final result event
3. Compare total_cost_usd with expected cost based on token counts and Anthropic pricing

Expected vs Actual

For a job with:

• Model: claude-haiku-4-5-20251001
• Input tokens: 18
• Output tokens: 2,435
• Cache creation tokens: 13,560
• Cache read tokens: 69,460

Expected cost (based on Anthropic pricing):

• Input: 18 × $0.80/1M = $0.000014
• Output: 2,435 × $4/1M = $0.0097
• Cache write: 13,560 × $1/1M = $0.0136
• Cache read: 69,460 × $0.08/1M = $0.0056
• Total: ~$0.03

Actual total_cost_usd returned: $3.67 (approximately 100x higher)

Aggregated over a day of jobs, we see ~$27 reported vs ~$2.60 calculated (~10x).

Environment

• Claude Code CLI version: latest (April 2026)
• Model: claude-haiku-4-5-20251001
• Output format: stream-json

Impact

This causes cost tracking/reporting to show wildly inflated numbers, making it difficult to monitor actual API spend.

Workaround

We're currently calculating costs manually from token counts, ignoring the total_cost_usd field.