Apple's usual strategy to "fix" prices is to not give retailers any room to work with. If they can't buy an iPad for much less than $499, they can't put it on much of a sale. Why sell it at all if the margins are so bad? Accessories and warranties!
This strategy doesn't work very well with iPhones, since there is a lot of excess carrier profit in the 24-month subsidies, above the $700 or so cost of the iPhone.
There's not as much profit as you'd think. And a lot less than lower priced phones from other manufacturers. Plus, the carriers have to assume a ton of risk by agreeing to buy millions of iPhones whether they sell or not. Verizon had an estimated shorfall of $12-14 billion dollars as of July of iPhones they'd have to buy even though they didn't have the sales to warrant it. Not sure how that would up.
Currently, AT&T charges you $199 for an iPhone 5S, then has to cover $19 of subsidy over the 24 months of the $80/month contract.
A new carrier could charge $99 for an iPhone 5S, and make a huge splash. That would require another $4 of subsidy per month, but it would be pretty easy to just raise their plan to $85. Since they aren't just a retailer selling a single product once, it's much easier to move costs around. Similar to how a car dealer can play games with funding to make a car cost less but not really cost any profit.
This strategy doesn't work very well with iPhones, since there is a lot of excess carrier profit in the 24-month subsidies, above the $700 or so cost of the iPhone.