add Elastic Managed LLM to observability billing

Author: mdbirnstiehl

deploy-manage/cloud-organization/billing/elastic-observability-billing-dimensions.md

@@ -25,3 +25,7 @@ Data volumes for ingest and retention are based on the fully enriched normalized
 [Synthetic monitoring](/solutions/observability/synthetics/index.md) is an optional add-on to Observability Serverless projects that allows you to periodically check the status of your services and applications. In addition to the core ingest and retention dimensions, there is a charge to execute synthetic monitors on our testing infrastructure. Browser (journey) based tests are charged per-test-run, and ping (lightweight) tests have an all-you-can-use model per location used.
 
 Refer to [Serverless billing dimensions](serverless-project-billing-dimensions.md) and the [{{ecloud}} pricing table](https://cloud.elastic.co/cloud-pricing-table?productType=serverless&project=observability) for more details about {{obs-serverless}} billing dimensions and rates.
+
+## Elastic Managed LLM
+
+The default [Elastic Managed LLM](kibana://reference/connectors-kibana/elastic-managed-llm.md) enables you to leverage AI-powered search as a service without deploying a model in your serverless project. It's configured by default to use with the Security AI Assistant, Attack Discovery, and other applicable AI features as a part of your "Complete" tier subscription. Using the default LLM will use tokens and incur related token-based add-on billing for your serverless project.