One of the best use cases for feature flags is testing monetization without shipping custom logic to every user cohort. I recently used Truflag to run a pricing experiment inside my NFL trivia app and the results were bigger than I expected:
9 months ago I shipped an NFL trivia app (Gridiron Trivia) and began monetizing it with in-app subscriptions/purchases in July. The business model is pretty similar to New York Times games: offer daily games for free (with ads) and offer collections of games for one-time purchase. Subscribers get the ad-free version and access to all game collections.