You can't buy an unlocked iPhone from Apple in the US. You can buy a contract-free iPhone for $600, which is more than the Nexus One and still locked to AT&T. Yes you may be able to unlock the iPhone yourself, but that gets you in a constant cat-and-mouse game with Apple who considers you a criminal at that point.

No non-technical user in his sane mind would pay $330 more for an unlocked phone.

T-Mobile's plans are $20/month cheaper if you're not paying off a subsidized phone, so you'll more than recoup the cost difference of the unsubsidized N1 over two years.