LLM pricing · Compare

Claude Sonnet 4.5 vs Gemini 3.8 Flash pricing (November 2026)

In short: Gemini 3.8 Flash is 4.0× cheaper than Claude Sonnet 4.5 per chat message: $0.0026 vs $0.0105 for a typical chat turn (1,500 tokens in, 400 out). On a $9.99 plan, a user can send about 3,234 messages a month on Gemini 3.8 Flash before they cost more than they pay, versus 808 on Claude Sonnet 4.5.

Price per million tokens

Claude Sonnet 4.5Gemini 3.8 Flash
ProviderAnthropicGoogle
Input$3$0.75
Cached input$0.3$0.075
Output$15$3.75
Long promptssame ratesame rate

Cost per message and per user

Claude Sonnet 4.5Gemini 3.8 Flash
Per message$0.0105$0.0026
Per message, prompt 2/3 cached$0.0078$0.0019
Light user (30 msgs/mo)$0.315$0.0788
Typical user (300 msgs/mo)$3.15$0.788
Heavy user (3,000 msgs/mo)$31.50$7.88
Break-even on $9.99808 msgs/mo3,234 msgs/mo

Red: the user costs more in AI than the $8.49 you keep from a $9.99 plan after a 15% store fee.

Which to use

Price is only half of it: pick the cheapest model that gives answers your users accept. Many apps route most traffic to the cheaper model and send only hard requests, or only paying users, to the stronger one. Whatever the mix, the number that decides your margin is cost per user, because a few heavy users usually drive most of the bill.

Try your own numbers

Cost per message
$0.0026
AI cost per user / month
$0.79
Margin per user / month
$7.70
Break-even messages / month
3,234

List prices, standard tier, prompts under the long-context threshold. Averages hide your heaviest users: FiscaLLM shows this per real user.

Track the real cost of each user

FiscaLLM prices every Anthropic and Google call with these rates, per user, and sets it next to what that user paid through RevenueCat, Stripe or a CSV. You see which users and which model lose you money. Free and open source. See the demo.

Questions

Is Claude Sonnet 4.5 or Gemini 3.8 Flash cheaper?

Gemini 3.8 Flash is 4.0× cheaper than Claude Sonnet 4.5 per chat message: $0.0026 vs $0.0105 for a 1,500-token prompt and a 400-token reply, at list prices.

How many messages can a $9.99 subscriber send on each?

About 808 a month on Claude Sonnet 4.5 and 3,234 on Gemini 3.8 Flash, before AI cost uses up what you keep after a 15% store fee.

Can I use both?

Yes. A common pattern is the cheaper model for most traffic and the stronger one for hard requests or paying users. Track cost per user to see whether the mix pays off.

List prices, standard tier. Batch, priority and regional pricing differ; check each provider for the latest.