Previous to this, all subscription price adjustment will be notified to the subscriber and requires their full consent to continue subscribe the service. However, Apple has updated the terms that allow developers to adjust subscription price without agreement from the end user. This is due to the factor that some users may lost out their subscription if they have missed the notification that requires their agreement.
However, some restrictions applies for developer. Developers can only increase price hike per month where maximum adjustment for normal subscription is capped at $5 and max adjustment per year is at $50. Developer will also need to notify end user on the price adjustment and allow users to easily cancel the subscription cost.