feat(cli): add token cost estimation per provider and make configurable

[chaitanyarahalkar]

What’s new

This PR adds optional, provider-aware cost estimates to the Goose CLI and addresses issue/feature request #2933
CLI tools like Claude Code have also started adding cost estimates to ensure that spending is tracked for the session.

Key points

1. Cost display (disabled by default)

   • New config flag GOOSE_CLI_SHOW_COST (or env-var) shows the dollar cost after each exchange.
   • No change to existing UX unless the user opts-in.

2. **Accurate per-provider tables based on current data for OpenAI, Anthropic and Google AI

3. CLI integration

   • When enabled, after the context-usage line the CLI prints

     Cost: $0.0123 USD (123 tokens: in 63, out 60)
     

   • Cost figures are estimated from the provider’s usage data. When using open weight models, the cost figures are not shown

4. Configurable & future-proof

   • Adding/changing rates only requires editing the table in session/output.rs.
   • Unknown models/providers simply omit the cost line.

Screenshot

How to enable

# one-off
GOOSE_CLI_SHOW_COST=true goose chat

# persistent
# ~/.config/goose/config.yaml
GOOSE_CLI_SHOW_COST: true

[michaelneale]

nice, LGTM

[michaelneale]

(will need to update, run cargo fmt and clippy etc)

[sambradbury]

This is similar to the changes here which add cost tracking the UI #2992

That MR doesn't handle the CLI as yours does but querying for updated pricing would be better than having to hardcode pricing here.

[patrickReiis]

Thank you very much 🙏🙏🙏🙏🙏

[DOsinga]

So yeah, since the other CL is merged and has actual price information rather than estimating it, I would suggest we use that infrastructure rather than adding our own estimates here

[DOsinga]

closing this for now - let me know if you want to pick it up again