Azure Log Analytics Pricing
Azure Log Analytics is a service within Azure and our On-Demand Assessment are hosted in Azure Log Analytics thus An Azure subscription is needed to use Azure Log Analytics. By linking your Azure Log Analytics workspace with the Services Hub, you can grant/remove access to the Azure Log Analytics workspace, enable your On-Demand assessments and have your data flow to the Services Hub for a seamless experience. You will want to investigate getting a subscription if you want to take advantage of On-Demand Assessments.
To learn pricing details specific to your region, see Azure Log Analytics Pricing.