JoomPush integrates directly with Firebase Cloud Messaging (which is free as of now) using which you can send unlimited Web Push Notifications to Unlimited subscribers, that's the best part of JoomPush. You will not have to pay any monthly service as long as you have an active subscription. You can still use the extension after the expiration of your subscription (on the exsisting installations) but you won't be entitled to get updates and support untill it is renewed. Do let us know if you have any more questions. We are happy to help.