At 4 requests/user/day (totaling 12,000 queries/mo), running Document summarization on Gemini 3.5 Flash (OpenRouter) costs $474.30 / month ($4.743 / user / mo).
Document summarization for a 100 active users (public launch) audience means 400 requests per day on average, each carrying 25,000 input and 600 output tokens at a 10% cacheable share — so the effective per-request cost on Gemini 3.5 Flash (OpenRouter) is $0.0395, of which $40.50/mo comes back from prompt caching. Per active user that's $4.743/mo — the number to hold against your pricing tier and gross margin. Charging at least $23.715/user/mo keeps gross margin at or above 80%.
Quick answer
For 100 Active Users, Document summarization on Gemini 3.5 Flash (OpenRouter) is modeled at 12,000 requests per month, costing $474.30 per month or $4.743 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 100 Active Users generating 12,000 queries.
Direct inference cost per MAU to model your SaaS pricing tiers and gross margins.
Savings generated by exploiting 10% cache hits on prompt context.
| Model | Provider | Monthly Spend (100 Active Users) | Cost / User / Mo | Annual Spend | Context Limit |
|---|---|---|---|---|---|
| Gemini 3.5 Flash (OpenRouter) (Current) | $474.30 | $4.743 | $5,691.60 | 1,048,576 | |
| GPT-5.6 Terra | openai | $632.40 | $6.324 | $7,588.80 | 1,050,000 |
| GPT-5.4 Workhorse | openai | $790.50 | $7.905 | $9,486.00 | 256,000 |
| o3-mini | openai | $345.18 | $3.452 | $4,142.16 | 200,000 |
| o4-mini | openai | $336.93 | $3.369 | $4,043.16 | 256,000 |
| o1-mini | openai | $345.18 | $3.452 | $4,142.16 | 128,000 |
At 4 queries per user/day with Gemini 3.5 Flash (OpenRouter), the estimated cost is $4.743 per monthly active user (MAU). Total monthly bill for 100 Active Users is $474.30.
Assuming a 10% cache hit rate on repeated system and context tokens, prompt caching saves $40.50 per month ($486.00/year) on Gemini 3.5 Flash (OpenRouter).
With a direct COGS of $4.743 per user/month on Gemini 3.5 Flash (OpenRouter), charging at least $23.715 per user/month ensures an 80%+ software gross margin.