YouTube charged $54.99 for in-app and $49.99 on their website. There are no rules against this.Source for this statement? As far as I know that would be against Apple's App Store policies. Unless something has changed, Apple required that In-App purchase be the same cost as purchases outside the App.

YouTube TV Increases Price to $49.99/Month, $54.99/Month When Billed Through Apple
YouTube TV today announced a price hike for all users, first hitting new subscribers immediately and then arriving for existing subscribers beginning...

You can find iTunes gift cards for 15-20% off several times a year, making it cheaper through IAPPeople will just stay signed up for the service just through the YouTube TV site and stay logged in on their Apple devices. You don't have to give up the service. Google was charging more for this on the App Store to make up the difference. Now anyone who wants the service and was on iOS will save 5 bucks a month.