Why are sprint, verizon and AT&T iphones cheaper?

I don't get it, are they g#contracts or something because i'm on AT&T and it says $0.99 for an iphone 4 8G! That seems abit too good to be true to be honest or am i missing something?

That is if you sign up with the 2 year contract you get that price, if not you would mostlikely have to pay full price of the phone which ranges from (200-500$)

Those phones are on contracts, meaning that the cost of the phone is made up over the course of the contract. Effectively the phone is on a two year loan to the consumer, and the loan is completed when the contract is completed.

If you start a contract just for the cheap phone, and stop paying on the contract, or do not pay the ETF, the carrier will place a negative mark on your credit, which can prevent you from getting a contract cell phone in the future, as well as hinder getting loans and higher paying jobs.