Hi @Ry Foo 

From Deezer Duo link :

Deezer Duo is our new subscription service that allows two people to have our premium features under one ownership - but better yet, at a reduced cost of 33% the value of two premium accounts.

All what you need to know about Deezer Duo you can see in link below 

https://support.deezer.com/hc/en-gb/articles/16545519017885-Deezer-Duo

The price of a Premium subscription depends on which country you are from.