@Piloti - troll much?
The £900 figure comes from expansys, who do like to rip people off by getting them to buy up front for phones they don't have. The white iphone will almost certainly cost the same as a regular iphone, which is £510/£612 for 16GB/32GB.
This compares to top-end Android smartphones, such as £429 for a 16GB Google Nexus-S, or £485 for a 16GB Samsung Galaxy S.
Whether you want to pay the additional money, or whether that money is well spent, is at the discretion of the purchaser.
If you have bought into the Apple media hierarchy, it may well be that other smart phone choices are idiotic - can the Galaxy S stream to Apple TV? Can it synch with itunes?
You may think these questions are ridiculous, but they are the very questions my old man asked me when I suggested upgrading his iphone to an android phone - he wants what he has got, but faster and better looking, and is not interested in learning a new platform. For him, an extra £100 is insignificant compared to it working how he expects.
Apple prices are from UK apple store, Android prices are from carphone warehouse.