Now the fun is *really* starting. AT&T has clarified their "unlimited" plan to mean 3GB
. Which is the same as their top (if a two-tier plan can have a "top") tiered plan.
First you should know that AT&T offers only 2 plans: a 300MB plan for $20 and a 3GB plan for $30. This shows a huge disparity if one calculates a "per byte" cost for each plan. Additionally, if one exceeds the tiered plan, additiona data is charged as $67/GB on the low tier and $10 on the higher tier - unthrottled. Again, a huge per byte pricing discrepancy.
Skeptics observe that there is no justification for the throttling in terms of "network quality", since the throttling does not take into account location, time, or any other qualitative factor - only data usage. They also note that since the unlimited plan costs the same as the 3GB a month plan, this means that effectively AT&T is trying to coerce users to pay more ($10/GB) for users who exceed the 3GB tier of data usage.
This means it is entirely a revenue grab, and has nothing to do with network quality. AT&T is using pricing to force every user onto their 3GB (and then $10/GB thereafter) plan, rather than having a two-tiered plan or even a 3-tiered plan with one tier being "unlimited".
Sprint advertising is correct in that they truly do offer an unlimited plan - but IIRC, that is at $50/month.
T-Mobile (where I moved to in February) offers 2GB vs 300MB AT&T pricing tier of $20 and then throttles data usage, whereas AT&T will hit you with a $20 per 300MB at their uncapped speed. Not a place I want to be price-wise. I like to know definitively how much my bill is going to be and I don't want to risk an overage that could wipe out my family budget if a kid does something stupid.
Do the math. If you sign up on the 300MB plan, by the time you have consumed 3GB of data it will cost you $174. This is the stick that AT&T use to "force" you to sign up for the $30/month 3GB plan. And since there is nothing in it for AT&T if your usage is over that, they throttle your speed to make you consider going to the equivalent-priced plan where they can charge you and get revenue if you go over.