So let's say you want to put 5 smartphones on a plan where 10GB a month in data is selected. 10GB is $120, plus $30 for each phone. That works out $270 per month. Feature phones will cost you $30 per device monthly, Laptops and Notebooks $20 per device monthly and tablets $10 per device monthly. Businesses who need data sharing for more than 25 devices can use the AT&T Business Pooled Nation for Data plans, with buckets ranging from 300 MB to 10 GB and monthly prices from $20 to $80 for eligible devices. And of course, each data plan gives the user free access at 32,000 AT&T Hot Spots
Yes, it feels like you're selecting dinner at your favorite Chinese restaurant, but these plans are flexible and allow you to construct the plan that you suits your needs.
source: AT&T via Engadget