[Eridrus]

Depends how you count it. The pricing structure of cell phones is pretty unfriendly in the US.

You can get a 1GB plan from T-Mobile for $50; or a $3GB plan for $60 or 5GB for $70 or unlimited for $80. [1]

So, the average cost is close to that $22/GB number, but the marginal cost is closer to $5.

You can find some prepaid voice+data plans, but their prices are not particularly competitive in the 2GB range.

I did find some cheaper data-only plans from T-Mobile at $10/GB[2], but that's not really what people are buying.

[1] http://www.t-mobile.com/cell-phone-plans/individual.html

[2] https://prepaid-phones.t-mobile.com/prepaid-internet

[maxerickson]

The so called Walmart plan is cheaper:

https://prepaid-phones.t-mobile.com/other-prepaid-plans

(And fairly popular as prepaid goes)