You can see this in action on Twitch sometimes in the chat. People ask why the subscription for a streamer via mobile app is $5.99 when it's $4.99 via the web app when there is no difference in what is being provided.

It is noticed and often people actively avoid the higher price once they are aware. Some are frustrated and unsubscribe.

This is understandable since they realize they've been paying an on-going 20% premium every month for a one-time convenience by originally pressing the subscribe button from the mobile version. And none of the extra 20% goes to the streamer they wanted to support.