So, the moral of the story is that it will cost you an additional 5% of the total cost of owning the iPhone 4 to get the better phone. That breaks down to around $4 extra per month of your contract.
In other words, when you consider it as part of the total cost of owning an iPhone, the extra $100 paid for the newer phone is a negligible expense.
This is a great post to send people to who complain about paying an extra $100 for the 4S over the 4.