[nodamage]

Both are relevant, because in order to successfully win an antitrust tying claim under US law you need to prove the seller had sufficient market power in a tying product in order to coerce buyers into buying the tied product.

In this case, once you buy an iPhone, you're forced to use Apple's system to make in-app purchases. The tying product is the phone, and the tied product is the in-app purchase.

So you need to show that Apple has sufficient market power in the smartphone market, and that is where the question of the ability to control prices of phones comes in.

[comex]

Epic's lawsuit does not accuse Apple of tying App Store sales to phone sales. Two of the nine counts are about allegedly tying in-app purchases to app sales, and the rest don't involve tying.

(Neither does Apple v. Pepper.)

[nodamage]

I wasn't actually talking about Epic's lawsuit.

But since you mentioned it, I'm not really sure that Epic will succeed with their argument that the "iOS App Distribution" market is the relevant tying product market absent an analysis of the overall smartphone market.