Update billing-management.mdx

Author: ingrid-wu

docs/account-management/billing-management.mdx

@@ -152,6 +152,9 @@ Task costs only apply in live deployments. Testing in the builder is always free
 | Tool         | Provider     | Rate                          |
 |--------------|--------------|-------------------------------|
 | GPT Image    | OpenAI       | $5 input, $10 image input, $40 output per 1M tokens |
+| Nano Banana    | GoogleAI   | $0.039 per request, $0.30 text/image input per 1M tokens |
+| Imagen 4       | GoogleAI   | $0.040 per request            |
+| Imagen 4 Ultra | GoogleAI   | $0.060 per request            |
 | HD 8 Steps   | Flux Schnell | $0.001 per request            |
 | HD 50 Steps  | Flux Dev     | $0.008 per request            |