I don't think the OP was saying that they'd definitely have to do so, but it's typically something companies do to increase market share generally speaking. Reduce price point means reducing profit margin, but often increasing market share because the lower price means more people can buy.
Apple typically hasn't done this (or certainly not to the extent other mfgs do) but certainly still like talking about their increasing market share.
Because you can now buy an Android phone for less than £100. If Apple want to compete with that they'll have to compromise on both quality and profit margin.
Right now Apple is only competing in the high end mid-sized slate smartphone segment. You're pointing out just 1 other smartphone segment that they could compete in, the lower priced segment. There are many ways Apple could compete. They could release 2 or 3 new styles of iPhones while retaining the same price.
Apple pride themselves on making the iPhone simple, and not fragmented. I can't see how they can do that and still release the iPhones in different styles, unless we're talking nothing more than different covers.
The massive market growth in smartphones is being caused by the smartphone becoming cheaper - if they want more of the market then they have to enter that area.
Very good question. For some reason having differentiation in the smartphone space is known as "Fragmentation" and bad.
Personally, I'd be very happy with Apple bringing out a wider mix of phones, but they seem dead against it.
Edit: Just seen your comment at the bottom of the page - I totally agree - Apple's lack of different options is probably going to go badly for them in the long run.
To make development easy and to make it easy create good user experiences across all iOS devices. None of their iOS devices have multiple versions in a single product cycle.
Apple typically hasn't done this (or certainly not to the extent other mfgs do) but certainly still like talking about their increasing market share.