How much does AT&T charge for Internet?

I'm wondering how much they charge to add a line… I'm on a family plan with my dad mom and brother and me and my brother have iPhone 3G and we wanna get Internet so how much would it cost to get Internet on our phones if we have a family plan? Please answer!

It depends. You can get data on each line so there would be 4 different data plans and each would be 10-50 a month. Check their website and see the mobile share plan