Currently, developers can change the price of VIP server subscriptions to anything they like. If the developer does this, however, all running subscriptions get cancelled. This is fair because this prevents abuse of the system and unexpectedly high subscription costs for the player if the price is increased.
My proposal is to only cancel the current subscriptions if the new subscription price is higher.
The result of this is that if the developer decides to make the VIP servers of their game cheaper, the developer still maintains all the running subscriptions. (And with the added benefit that current subscription owners get charged less.)
