To be fair to OP, Apple makes it dead easy to see how much the IAPs are for a given app (in the case of this one, $2.49 monthly or $24.99 yearly).
> it's not displayed on the App Store description either.
Developers don't need to (and, imo, shouldn't) put pricing in the App Store description, because that's what the auto-generated "In-App Purchases" list is there for.