As of April 2018, any newly onboarded Log Analytics workspace will now be on consumption-based pricing.  If you have pre-April 2018 workspaces setup, you can continue with them or move to the new pricing model.  In this video I go over the licensing change in Azure OMS Log analytics.  I also go over how to get an estimate of the new pricing and show you how to convert an existing workspace to the new pricing plan.

More information can be found here:

https://azure.microsoft.com/en-us/pricing/details/log-analytics/
https://docs.microsoft.com/en-us/azure/monitoring-and-diagnostics/monitoring-usage-and-estimated-costs
https://azure.microsoft.com/en-us/blog/introducing-a-new-way-to-purchase-azure-monitoring-services/