SQL Server is a different beast. You get alot of performance enhancement out of box. Yes its costs money you save tremendous amount of tweaking time and headaches.
or you can just use AzureSQL and essentially just pay what it costs for the box, because it is platform as a service. Its far cheaper (and easier to maintain) than what it'd cost to buy a SQL Server license and run it on a VM.
That is a 10 cal license, so you can only have 10 users using it, and that is 10 assigned users. Don't quote me on that but you have to use core licenses for web apps if you have internet users.