To do either of these things, the user would need to be enrolled in Apple’s developer program which costs $99/year. These terms are implicitly part of your terms, meaning that it’s basically equivalent to you charging $99/year for the user to make modifications.
Not any more than targeting your app at the iPhone requires the user to buy an iPhone, thus being equivalent to charging $700...
It is more, because the cost is incurred when you try to exercise your rights. The GPL allows costs to obtain the work in the first place. Otherwise there could be no GPL for software that runs on computers that cost money.
Once the costs are incurred for obtaining the work, there can only be nominal charges for replacing the LGPL covered library (cost of media, for example, is ok).
The alleged problem is not in access to source code of the app or library, but is in users inability to recombine modified LGPL piece with the app itself to produce new work. A user who wants to modify the LGPL piece of an app would have to pay the dues to Apple to make use of thusly modified app, and this is deemed to violate the "no fees imposed" clause.
Not any more than targeting your app at the iPhone requires the user to buy an iPhone, thus being equivalent to charging $700...