You are comparing AT&T to the other large carriers, all of which are rip offs. Compare it to MVNOs and you'll see the huge difference.
I looked into 4 or 5 of the top-rated MVNOs a few months ago but there were just so many gotchas. They were on a crappy network, or didn't offer unlimited data, or were only 3G, or were 4G but not LTE, or wouldn't allow me to use a new model iPhone, or would allow me to use a new iPhone but some features wouldn't work, or didn't actually save me money once you account for all the data I use, etc etc.
I know there are hundreds of MVNOs but that's just way too many for me to check out; when 100% of the top-rated MVNOs had significant problems like those I listed, I assume the others are even worse.
I've also tried two MVNOs, Red Pocket and NetZero. Red Pocket I could never get to even activate and work...their customer support was nearly non-existent. NetZero I was able to activate, but they had terrible coverage. And even when it looked like I had a good connection, it was a lie--I didn't.
But I am open to being corrected. If you can find me an MVNO that works on a solid network (AT&T, Verizon, T-Mobile are all fine where I live), has customer support, doesn't have any of those weird gotchas, and saves me money, I'll switch. AT&T's recent price increase to the unlimited plan means that, for a limited time, I can leave my contract without penalty.