At 40 requests/user/day (totaling 6,000,000 queries/mo), running AI coding assistant on o3 (Reasoning Frontier) costs $811,200.00 / month ($162.24 / user / mo).
AI coding assistant for a 5,000 active users (growth stage saas) audience means 200,000 requests per day on average, each carrying 12,000 input and 2,000 output tokens at a 60% cacheable share — so the effective per-request cost on o3 (Reasoning Frontier) is $0.1352, of which $388,800.00/mo comes back from prompt caching. Per active user that's $162.24/mo — the number to hold against your pricing tier and gross margin. Charging at least $811.20/user/mo keeps gross margin at or above 80%.
Quick answer
For 5,000 Active Users, AI coding assistant on o3 (Reasoning Frontier) is modeled at 6,000,000 requests per month, costing $811,200.00 per month or $162.24 per active user.
Method & trust
This projection combines the selected active-user tier, requests per user per day, input/output tokens per request, and the modeled cache share. It is an operating estimate, not a provider invoice; production traffic and retries should be measured against it.
Total expected API invoice for 5,000 Active Users generating 6,000,000 queries.
Direct inference cost per MAU to model your SaaS pricing tiers and gross margins.
Savings generated by exploiting 60% cache hits on prompt context.
| Model | Provider | Monthly Spend (5,000 Active Users) | Cost / User / Mo | Annual Spend | Context Limit |
|---|---|---|---|---|---|
| o3 (Reasoning Frontier) (Current) | openai | $811,200.00 | $162.24 | $9,734,400.00 | 1,050,000 |
| GPT-5.6 Sol | openai | $525,600.00 | $105.12 | $6,307,200.00 | 1,050,000 |
| GPT-5.6 Cyber | openai | $1,314,000.00 | $262.80 | $15,768,000.00 | 1,050,000 |
| GPT-5.5 Standard | openai | $525,600.00 | $105.12 | $6,307,200.00 | 512,000 |
| GPT-5.5 Pro | openai | $3,153,600.00 | $630.72 | $37,843,200.00 | 512,000 |
| o3-pro (Frontier Reasoning) | openai | $1,622,400.00 | $324.48 | $19,468,800.00 | 1,000,000 |
At 40 queries per user/day with o3 (Reasoning Frontier), the estimated cost is $162.24 per monthly active user (MAU). Total monthly bill for 5,000 Active Users is $811,200.00.
Assuming a 60% cache hit rate on repeated system and context tokens, prompt caching saves $388,800.00 per month ($4,665,600.00/year) on o3 (Reasoning Frontier).
With a direct COGS of $162.24 per user/month on o3 (Reasoning Frontier), charging at least $811.20 per user/month ensures an 80%+ software gross margin.