You logic is flawed. MacBooks and mac computers have existed far long more than iPhone and their price isn't getting lower. I fail to see why the iPhone, another great premium Apple product, will drop it's price in the future.
Um yes they have. Today you can buy a pretty good spec MBP for $1500. 4 years you'd be spending $3-4k+.
The same applies to Windows laptops. I bought a 17" Dell Inspiron 9400 in 2005-06 for A$3k (actually it was a $4k spec where 2 coupons collided bringing it to about $2.8k). At that time a similar MBP was A$4.5k.
This year I specced a 15" Dell for my sister for $1k. A gaming laptop is under A$2k. My 2009 13" MBP cost A$1800. The top (base) MBP is <A$3k.
Macs have a gentler slope of price decreases as Apple tends to increase the (relative) spec ate the same time but it's a complete lie to say they haven't dropped price.
IMHO the iPhone will be no different.
In fact the first iPod Touches were more expensive than the current batch so it already has happened.
