How much will it cost to upgrade to an iPhone?

I've had my lg xenon since may2009 and I want to upgrade early to the iPhone 3Gs (16gb). How much would that be to change phones early?

Thanks.How much will it cost to upgrade to an iPhone?
It would cost $399 for the 16gb and you would have to sign a new contract. A better idea is to wait and see whether AT%26amp;T will offer incentives to upgrade when the iPhone HD is released in June.How much will it cost to upgrade to an iPhone?
to above answer..

the iphone HD isnt a phone its software.

still same IphoneHow much will it cost to upgrade to an iPhone?
Why u wanna pay it when someone giving its for free....I didnt got one with them..seems am not that lucky..But u can try it ,if u have luck u may get one ....http://www.simplyfreeiphone.co.uk/