Claude Code vs GPT-5.6 Sol vs Grok 4.5: Cost Per Completed Coding Task (July 2026)
By Eric Bush · July 10, 2026 · 10 min read
Three Contenders, One Question
July 2026 gives developers three strong options for AI-assisted coding at different price points: Claude Code (powered by Opus 4.8 at $5/$25 or Sonnet 5 at $2/$10), GPT-5.6 Sol ($5/$30), and Grok 4.5 ($2/$6 base, $4/$18 fast mode). The question isn't which scores highest on benchmarks — it's which delivers the lowest cost per task that actually ships.
A "completed coding task" means different things in different contexts. This comparison defines three categories — bug fixes, feature additions, and refactors — estimates realistic token usage for each, and calculates what you actually pay per successful outcome when factoring in failure rates and retries.
Defining a "Completed Coding Task"
We use three representative task types that cover most daily developer work:
- Bug fix: Diagnose and resolve a reported issue. Typically involves reading error context, identifying root cause, applying a fix, and verifying tests pass. Average: 20K input tokens, 4K output tokens per attempt.
- Feature addition: Implement a well-specified new feature (new endpoint, UI component, integration). Requires reading existing patterns, generating new code, and updating tests. Average: 40K input tokens, 10K output tokens per attempt.
- Refactor: Restructure existing code without changing behavior. Involves understanding the full scope, making coordinated changes across files, ensuring nothing breaks. Average: 50K input tokens, 12K output tokens per attempt.
"Completed" means: code works, tests pass, no regressions, ready for code review. Partial completions that need human fixup count as failures for this analysis.
Raw Cost Per Attempt
Before factoring in success rates, here's what each attempt costs:
Bug Fix (20K in / 4K out):
- Claude Code (Opus 4.8, $5/$25): 20K × $5/M + 4K × $25/M = $0.10 + $0.10 = $0.20
- Claude Code (Sonnet 5, $2/$10): 20K × $2/M + 4K × $10/M = $0.04 + $0.04 = $0.08
- GPT-5.6 Sol ($5/$30): 20K × $5/M + 4K × $30/M = $0.10 + $0.12 = $0.22
- Grok 4.5 base ($2/$6): 20K × $2/M + 4K × $6/M = $0.04 + $0.024 = $0.064
- Grok 4.5 fast ($4/$18): 20K × $4/M + 4K × $18/M = $0.08 + $0.072 = $0.152
Feature Addition (40K in / 10K out):
- Claude Code (Opus 4.8): 40K × $5/M + 10K × $25/M = $0.20 + $0.25 = $0.45
- Claude Code (Sonnet 5): 40K × $2/M + 10K × $10/M = $0.08 + $0.10 = $0.18
- GPT-5.6 Sol: 40K × $5/M + 10K × $30/M = $0.20 + $0.30 = $0.50
- Grok 4.5 base: 40K × $2/M + 10K × $6/M = $0.08 + $0.06 = $0.14
- Grok 4.5 fast: 40K × $4/M + 10K × $18/M = $0.16 + $0.18 = $0.34
Refactor (50K in / 12K out):
- Claude Code (Opus 4.8): 50K × $5/M + 12K × $25/M = $0.25 + $0.30 = $0.55
- Claude Code (Sonnet 5): 50K × $2/M + 12K × $10/M = $0.10 + $0.12 = $0.22
- GPT-5.6 Sol: 50K × $5/M + 12K × $30/M = $0.25 + $0.36 = $0.61
- Grok 4.5 base: 50K × $2/M + 12K × $6/M = $0.10 + $0.072 = $0.172
- Grok 4.5 fast: 50K × $4/M + 12K × $18/M = $0.20 + $0.216 = $0.416
Success Rates Change Everything
Raw cost per attempt is misleading without success rates. Based on community reports, internal testing, and adjusted SWE-Bench data for July 2026, estimated first-attempt success rates for typical production tasks:
- Claude Opus 4.8: ~75% bug fixes, ~65% features, ~60% refactors
- Claude Sonnet 5: ~65% bug fixes, ~55% features, ~50% refactors
- GPT-5.6 Sol: ~72% bug fixes, ~63% features, ~58% refactors
- Grok 4.5 base: ~55% bug fixes, ~45% features, ~40% refactors
- Grok 4.5 fast: ~62% bug fixes, ~52% features, ~48% refactors
These are estimates for real production codebases — not benchmark performance. Your actual rates will vary by codebase complexity, documentation quality, and test coverage.
Cost Per Completed Task (The Real Comparison)
Dividing cost per attempt by success rate gives cost per completed task. For the feature addition category (the most common substantial task):
- Claude Code (Opus 4.8): $0.45 / 0.65 = $0.69 per completed feature
- Claude Code (Sonnet 5): $0.18 / 0.55 = $0.33 per completed feature
- GPT-5.6 Sol: $0.50 / 0.63 = $0.79 per completed feature
- Grok 4.5 base: $0.14 / 0.45 = $0.31 per completed feature
- Grok 4.5 fast: $0.34 / 0.52 = $0.65 per completed feature
The ranking shifts dramatically from raw pricing. Grok 4.5 base and Claude Sonnet 5 tie for best value at ~$0.31-$0.33 per completed feature. GPT-5.6 Sol — despite strong success rates — lands most expensive due to high output token pricing ($30/M).
The Hidden Variable: Time Cost
Cost per completed task ignores developer time. Factor in:
- Retry overhead: A 45% success rate means half your tasks need a second attempt. Each retry costs context-switching time (5-10 min) plus waiting for the second run.
- Review complexity: Premium models tend to produce more coherent, review-ready code. Fixing partial completions from cheaper models can eat 15-30 minutes.
- Latency: Grok 4.5 fast ($4/$18) costs more than base but returns results ~2x faster, potentially saving developer wait time worth $50-100/hr.
If your engineers cost $80/hr and each failed attempt wastes 15 minutes of their time ($20), add that to the per-task cost of lower-success-rate models:
- Grok 4.5 base (55% failures × $20): adds $11 waste per completed task
- Claude Opus 4.8 (35% failures × $20): adds $7 waste per completed task
When developer time is factored in, higher-success-rate models become relatively cheaper than pure token cost suggests.
Optimal Strategy by Team Size
Solo developer / indie hacker: Claude Sonnet 5 ($2/$10) offers the best balance. Decent success rates (55-65%), low per-attempt cost, and you're already handling retries manually. Monthly spend: $30-$100 for moderate usage.
Small team (3-8 devs): Tiered approach. Use Grok 4.5 base ($2/$6) or Sonnet 5 for routine tasks, escalate to Opus 4.8 for complex multi-file changes where first-attempt success saves coordination time. Monthly spend: $500-$2,000.
Mid-size team (10-25 devs): The developer-time factor dominates. Claude Opus 4.8 or Grok 4.5 fast become more justifiable because retry overhead across many developers adds up. Monthly spend: $3,000-$15,000.
July 2026 Verdict
Pure token economics: Grok 4.5 base ($2/$6) and Claude Sonnet 5 ($2/$10) deliver the lowest cost per completed task for most workloads. GPT-5.6 Sol's $30/M output pricing makes it the most expensive per task despite strong capabilities.
When developer time matters: Claude Opus 4.8 provides the best ROI for high-value engineering time because its higher success rates reduce retry overhead. The premium is a productivity investment, not just a quality one.
The recommendation: start with Sonnet 5 or Grok 4.5 as your default, measure your actual success rates for one sprint, then calculate whether Opus or Sol's higher rates justify the premium for your specific codebase and team. Don't trust benchmarks — trust your own data.
Want to calculate exact costs for your project?
Frequently Asked Questions
Which model has the lowest cost per completed coding task in July 2026?
Grok 4.5 base ($2/$6) and Claude Sonnet 5 ($2/$10) tie at approximately $0.31-$0.33 per completed feature task when factoring in their respective success rates. GPT-5.6 Sol is most expensive at $0.79 due to high output token pricing.
How much does a typical coding task cost with Claude Code using Opus 4.8?
A feature addition with Claude Code on Opus 4.8 ($5/$25 per M tokens) costs approximately $0.45 per attempt with an estimated 65% first-attempt success rate, resulting in $0.69 per completed task. Bug fixes are cheaper at roughly $0.27 per completed task.
Does a cheaper model always cost less per completed task?
No. A model with 45% success rate effectively needs 2+ attempts per task, doubling the token cost and adding developer wait time. A more expensive model with 75% success rate can cost less per completed task when you factor in retries and developer time.
How do I estimate my team's monthly AI coding budget?
Count your daily coding tasks per developer (typically 5-15 substantial tasks), multiply by cost per completed task for your chosen model, and factor in a 2-3x multiplier for context reading, exploratory queries, and retries. A solo dev on Sonnet 5 typically spends $30-$100/month; a 10-person team on Opus 4.8 may spend $3,000-$15,000/month.
Should I use Grok 4.5 base or fast mode?
Base ($2/$6) for async tasks where latency doesn't matter — batch code generation, test writing, documentation. Fast mode ($4/$18) when developers are actively waiting on results and their time costs more than the token premium. Fast mode also shows higher success rates (~52% vs 45% for features) due to increased inference compute.
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