docs: add USD pricing callout and clarify currency in billing threshold (#75307)

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: Kat Wilson <markhamka@gmail.com>

Author: 3 people

docs/platform/cloud/managing-airbyte-cloud/manage-credits.md

@@ -113,4 +113,12 @@ To unenroll, [email the Billing team](mailto:billing@airbyte.io) with your reque
 
 ## Purchasing credits
 
-Airbyte Cloud uses in-arrears billing, so you're invoiced monthly. If you want to pre-purchase credits, [contact Sales](https://airbyte.com/company/talk-to-sales).
+:::note
+
+All pricing is in USD.
+
+:::
+
+Airbyte Cloud uses in-arrears billing, so you're invoiced monthly. If you pass $2,000 (USD) in credit usage during a billing period, Airbyte automatically charges your saved payment method and issues an invoice.
+
+If you want to pre-purchase credits, [contact Sales](https://airbyte.com/company/talk-to-sales).