A perfect example of this is an app called "DayCount". The app's concept is very simple, enter a date, and the app will tell you either how many days until this date, or how many days have passed since this date. When you open the app for the first time you're immediately presented with a "Pro" version, for $3.99/month.
And almost every app does it now, many are "free" but as soon as you open it you realize that you actually have to "subscribe" to the app. Now don't get me wrong, some apps work great with this model. I just happily paid 1Password for another year of service, but 1Password is a genuinely useful application, and they keep my passwords, and paying them $2/mo to take care of this is a great deal in my opinion.
But what kind of value does a "day counting" app add that would warrant an annualized price of $48? I will say that DayCount is better than others, because it actually does something. I once saw an "Emoji Keyboard", a re-implementation of the default emoji keyboard, offered for $9.99/month.
Apple needs some more rules around what is and isn't allowed with iAP purchases. Subscriptions should have extra scrutiny put on them, make sure they actually add value and don't just extract money from users.
Hell it might be a good idea to nuke "Subscriptions" entirely. I get Netflix, Hulu and other services that give you ongoing value. But the notes app you threw together in half an hour using tutorials on Youtube does not deserve to charge $4.99/month for it's "Pro" version.