You can use the Azure Monitor pricing calculator to estimate costs, the bulk of which comes from the data ingestion costs and retention for your Azure Log Analytics workspaces and Application Insights resources. As monitoring costs tend to fluctuate, it is a good idea to first enable monitoring for a small number of resources and use observed data volumes with the calculator to estimate the costs for the entire environment. You can also use log queries in the Azure Log Analytics workspace and use the columns _IsBillable and _BilledSize to assist in analyzing billable data.