This is way beyond the original point being made, but in the YT app, the button to view channels that a user has subscribed to is indeed labelled "subscriptions".
I agree that in this context, the natural interpretation of the word is that money has been invested.
If you subscribe to a YT channel, you would just say you subscribe to the channel or you are a subscriber. You wouldn't say you have a "subscription" with the channel. That makes no sense.