Hello,
This is a community forum for technical questions & issues.
For question regarding pricing / licensing please contact a Microsoft sales partner or licensing expert.
Call (1-800-426-9400), Monday through Friday, 6:00 AM to 6:00 PM PST to speak directly to Microsoft licensing specialist.
See also eBook "SQL Server 2017 Licensing Guide"
https://download.microsoft.com/download/B/C/0/BC0B2EA7-D99D-42FB-9439-2C56880CAFF4/SQL_Server_2017_Licensing_Datasheet.pdf
And a web application is a Multiplexer scenario:
https://download.microsoft.com/download/8/7/3/8733d036-92b0-4cb8-8912-3b6ab966b8b2/multiplexing.pdf