Yay! I'm below average... I consider myself to be very, VERY lucky. My total wireless bill comes to just under $70/month and I have an iPhone 4 (soon to be an iPhone 5). I have so many legacy and grandfathered AT&T plans it's ridiculous...
Voice: 250 peak, 1000 off-peak -- $30/month *** Legacy ***
Texting: 200 messages -- $5/month *** Grandfathered ***
Data: Unlimited data for iPhone -- $30/month *** Grandfathered ***
From what I understand, if I upgrade to the iPhone 5, all of these plans will carryover to the new phone. I've heard that AT&T is doing this to keep those of us with unlimited data from jumping to another provider. Granted iPhone 5 users will be throttled after 5 GB.
The voice plan was something I've been able to hang on to since I signed up with Cingular Wireless. The phone I got at that time was a Motorola V551 flip-phone.