I have a Verizon plan. Unlimited minutes and messages (I think... I don't use messages...), 6gb of data shared across three 4g devices (iphone, ipad, ipad mini). I get some workplace discount (18% on my monthly bill, I think).
I pay $145 per month.
Not sure how. I add all the charges I should be paying and it should be less. But there are hidden fees, taxes, etc.
It's not cheap. But 4g is fast, coverage is good, 6gb of data is good for a boring bastard like me that watches very little video. Plus I have wifi at work and home... so I actually usually hit 2-3 gb per month.