Of course, it is. Maybe. It could be. I don’t know. Cal does:
Apple maximizes profits via higher prices and large gross margins. While Apple does not set prices, on the App Store it sets minimum prices, and price increments. Plus, Apple sets a higher than high barrier to entry by blocking third party opportunities to compete with the App Store, and remains a Single Seller for almost all iPhone and iPad customers.
Monopolies, of course, are not illegal but Apple owns more than one.