Starting May 1, 2024, stateful log search alerts, a feature which is currently in public preview, will be generally available, and so will become chargeable, with pricing details on the Azure Monitor Pricing page.
Log search alerts are a type of alert that you can use in Azure Monitor. They let you run a log analytics query on your logs at a regular interval and trigger an alert based on the results. To learn more about alerts and state, see Overview of Azure Monitor alerts - Azure Monitor | Microsoft Learn.
Once stateful log search alerts are generally available on May 1, 2024, stateful log search alerts pricing will be aligned with the pricing of stateless log search alerts. This means that, for both types of alerts, you will be charged based on the number of log search alert rules created, the frequency of evaluation, and the number of time series evaluated. You can find more details on the Azure Monitor Pricing page.