You're obviously an investment guru... /sarcasm
Ponying up something extra like this is like buying a Lexus when a Toyota will do, or not sealing up your home to save on AC bills, or buying a Mac Pro if you only need an iMac.
So what, I do go out and drop $60 on a dinner, or $50 at a bar. But this is an added, fixed, contractual expense, that's almost half as much as a car lease. (My Accord = $1500 down, $200/mo.).
Would I pay $600 for an Apple PDA/iPod, without the data plan? Sure. If I can, I'll do it the day it comes out. Will I give up a new Macbook 2 years down the line ($1080) just so I can be cool? No thanks. I don't NEED internet everywhere, I already pay for it at home.
I'll admit, I seriously did consider getting an iPhone. Having wikipedia in the palm of your hand, not needing to carry around my laptop and iPod everywhere I went, multi-touch, yes, it's very neat.
In fact, I'm still considering it.
But if I need to pony up $600 (when i could settle for a Treo for $99) and an exorbitant plan, I'll go with the Treo. $45/mo. saved is $45/mo. earned.