Okay, but I can see the price of Netflix and Spotify. Or are the prices different on iPhone? I don't have one, so I'm only going on what you're saying.
If Netflix did offer in-app subscription (through Apple), and charged it at a higher rate to account for Apple's cut, it would be forbidden from telling it's more expensive because Apple takes a cut, or that it's available for cheaper on their website. Apple even forbids Netflix emailing their customer after signup telling them it's cheaper on their website.
I think that has changed now for Netflix in particular, but not for some other types of apps?