Subscriber numbers do affect the amount to content providers. On the one hand, the content contracts are mainly fixed value. On the other hand, Netflix aims for a target margin and anything above that is spent. So if they get forecast more income then they budget to spend more while hitting their margin target.
Netflix margin structure and growth
Our US contribution margin structure is set mostly top down. For any given future period, we estimate revenue, and decide what we want to spend, and how much margin we want in that period. Competitive pressures in bidding for content would lead us to have slightly less content than we would otherwise, rather than overspending. The same is true for our marketing budget. The output variable is membership growth that those spending choices influence.