Why would someone buy a 4 cylinder Honda Accord when the 6 cylinder is faster? Why would you buy an 08 car after the 09s came out? Why buy last years Mac Pro 2.8 octo after the new Mac Pro as come out?
If you are a technology demon, then yes, get the newest and best with less regard for the price. But, most people don't care, don't use what they have to it's fullest potential, and would rather save a few bucks, than buying what they don't feel they need.
If you follow this logic through, you would find that this works on other choices you make in life. Things that are not as important to you, you will buy the cheaper option. With the iphone, you just can't say "it's only $100 more". If you do the math, that's double the price.
My wife and I make a good income, and I saw no need to spend the extra $100 on something she would never notice. Other things that are more important to her, I would spend the extra money.