How much does an iPhone 4/4S cost per month?

My mom tried to tell me that it would cost at least $150/month to have an iPhone. That seems a bit extreme because so many people have them. I would definitely want unlimited texting but i don't care about minutes because I don't talk on the phone that much. I'm hoping to split the monthly cost with my parents. Could you please list the possible plan choices? I need a rough estimate of a total.

Can you hook up a Sprint Iphone 4 to T-Mobile?

I'm buying a Iphone 4 from sprint and my carrier is T-mobile. Is there anyway I can hook up that Sprint phone to my T-mobile network? Or would I have to purchase a different company's iphone? (unlocked)

IPhone Composite cable not working?

I just got a composite cable for my iPhone 4 to connect to my tv and when I plug it in I just get sound no picture. Why is this? What am I missing? Do I need to do something on my iPhone first? Also I have iOS 6

What is the best portable ipod/iPhone boombox?

Money no object. Preferably AM/FM Radio. Good battery life. Recharges ipod. Plug in mains power. Rugged good build quality. Not to heavy. Very loud!
Looked at TDK 3 speaker system, JVC Kaboom, Pioneer Steez, Lansonic, Altec Lansing, Bose, Sony, Marley bag of rhythm, Sharp.
What's the best? So much choice it's hard to compare them all.

How to call from the us to Australia?

I really need help, my girlfriend is in Australia and I'm in the USA and I need to be able to call her. We both have iPhone 4S, I have sprint, I live in Oregon and she lives in Tasmania. Any help would be greatly appreciated, I don't wanna text or video chat, just call. Any apps or tips on what numbers to dial and prices would be greatly appreciated.

Iphone 4 camera.front and back?

Does the I phone 4 have a front and back camera?

Added (1). I did smart one. You aren't here with me so you don't know what I've done and what I haven't.