If you are still running SQL Server 2008/2008 R2, you probably have heard by now that as of July 9, 2019, you will no longer be supported. However, realizing that there are still a significant number of customers running on this platform that will not be able to upgrade to a newer version of SQL before that deadline, Microsoft has offered two options to provide extended security updates for an additional three years.
The first option you have requires the annual purchase of “Extended Security Updates.” Extended Security Updates will cost 75% of the full license cost annually and also requires that the customer is on active software assurance, which is typically 25% of the license cost annually. So effectively, to receive Extended Security Updates you are paying for new SQL Server licenses annually for three years, or until you migrate off SQL Server 2008/2008 R2.