For all your Windows Server 2008/R2 and SQL Server 2008/R2 workloads on Azure VMware Solutions, you get Extended Security Updates at no additional charge for 3 years.
https://azure.microsoft.com/en-us/pricing/details/azure-vmware/#pricing
You need to pay for other SQL Server and Windows Licenses but you can use AHB to utilize your existing licenses to reduce the cost.
https://azure.microsoft.com/en-us/pricing/hybrid-benefit/#overview
As a summary
The Azure VMware Solution (AVS) offers an Azure Hybrid Benefit (AHB) for SQL Server, which allows customers to utilize their existing paid SQL Server Enterprise licenses with active Software Assurance. This provides unlimited virtualization through SQL Server licenses on AVS, which can be managed via the Azure portal to create and implement VM-Host affinity placement policies.