Apple doesn't charge any premium anymore. iPhones are the same price as any other high-end flagships from reputable OEMs whether subsidised or unsubsidised. Ditto for most tablets outside the nexus line. And even Macs.
Android isn't exactly a saint either, neither is Windows Phone. Software development in general has taken a ship first, fix later approach across the board.
Apple has a reputation for taking the lion's share of money from the entire smartphone market for a reason. An iPhone 6 costs them $234 to manufacture and they charge a minimum of $650 for it. And the only difference between a 16gb memory module and a 128gb memory module is about $20, but Apple rakes in over $300. People pay, so Apple can charge as they see fit. Android OEM's try the same thing and that lasts for a few months before we see the price drop. They are just way to many choices in Android land compared to Apple land. You want an iPhone, you only have one option. And even though I have bought 2 iPhone 6's (64gb versions), I still think they overcharge. Examples:
$100 was the price you had/have to pay to go from 16gb to 32gb on an iPhone. Not a good deal. In fact, a complete rip-off. Android charged less than $50 to upgrade.
$100 is the price from 16gb to 64gb on an iPhone. Still not a good deal.
$200 for 16gb to 128gb a pretty good deal, but most people don't want to pay over $1000 for a phone.
Apple has and likely always will overcharge for memory for some reason. Even on the computer RAM.