[0] http://www.wolframalpha.com/input/?i=%28land+area+of+the+us+... (I excluded Alaska because most of that state doesn't have cellular coverage and the parts that do make up for the parts of the mainland that don't.)
[1] https://www.cricketwireless.com/cell-phone-plans
[2] http://prepaid-phones.t-mobile.com/prepaid-plans#other-month...
The last 12 months has seen more price competition ($40 a month on T Mobile is the data equivalent of your plan, with unlimited voice (that's the no contract plan)).
An example of how successful the marketing has been, people regularly talk about the subsidy they get from the phone company to buy their phone. It's really a contract where they end up paying more than the price of the phone (plus interest), but it still gets called a subsidy.
Some of my East European friends make me positively jealous with their cheap and very fast internet speeds compared to those in the UK.