Because JordanN's too big of an idiot for Deathawk to bother with, I figure I'll give this a shot. I'm no mac fanboy, nor will I ever be, but Deathawk has good points. Here's how I see it:
iPhone: 400$ + 60$ for the most basic plan listed there.
460$.
Now, let's match the iPhone's features with other things.
Nintendo DS - ~150$
Cartridge thing for playing movies/music etc - 75$ according to JordanN, but I'm not sure about the space on one of them. I've tried looking, but am unable to find how much it has. According to deathawk in a previous post, it's 2GB, so I'll go by that. 75 x 4 (to match the iPhones 8gigs) = 300$.
For a 2 megapixel camera phone, I've got about 100$.
For the headphones that come with the iPhone (which include a microphone for handsfree use of the phone) it's 25$, and the wouldn't even be compatible with your other phone, so that feature would be lost entirely.
OS X (included on the iphone) costs 100$, but wait! You haven't got anything to run it on. More features lost.
So, that pretty much sums up the purchasable features of the iPhone. Let's see, that's a grand total of... 675$. OH WAIT, THAT'S MORE THAN THE iPHONE. Not to mention the features you lost in the process, as well as the other features I haven't even mentioned (custom apps, free software upgrades, bluetooth, TV out, and more). Not to mention that now you've got 7 pieces of equipment, several of which are totally and utterly incompatible with each other.
iPhone seems like a decent deal to me.