A new capacity reservations pricing model for Azure Monitor Log Analytics is now available. With this new model, you pay a fixed fee based on the capacity tier you select for data ingestion. The capacity tiers start at 100 GB per day and provide a discount of up to 25 percent compared to Pay-As-You-Go. There are no changes to the existing Pay-As-You-Go model. The new pricing model will be available starting November 1, 2019.
For more details, read the Log Analytics section in the Azure Monitor pricing page and documentation.
Documentation
Azure Monitor pricing page