Working out how big a subscription you need comes down to one question: how many screens. Not how much content, not how many playlists, not how many people log in. The count that matters is the number of screens you are running.
This makes growth easy to reason about. Add a screen to a new lobby or a new production line, and you add a license. Retire a screen, and its license frees up. Your subscription rises and falls with the size of your fleet, and nothing else.
It also means you can plan ahead. If you know you are rolling out twenty screens next quarter, you know exactly what that adds. The cost of scaling is the cost of the screens, with nothing hidden in the content or the team behind them.