I can partially see AT&Ts side on the tethering. Data usage on a phone, or even an iPad is going to be less then data usage on a laptop.
Like Bitt said, I don't think that's the point. The point is that you are paying for 2GB of bandwidth for a month. It doesn't matter how you use that data connection, you paid for it. If they've done the math and concluded that the most bandwidth they can handle is 2GB, then they should do the opposite of what I suggested in my first post: make the "Data Pro" plan 1GB, and if you pay for tethering, you get 2GB.
If I burn through my 2GB in a month, then start charging me overage.
Continuing from the idea that it shouldn't matter if you use all the data, it also shouldn't matter how quickly you use it. Everybody's billing periods don't all start on the same day each month, so usage is staggered. So again, it's a matter of AT&T not wanting you to use it. If it's a strain on their network to have all 2GB used, they should reflect that in their plans.
I never said I didn't like the idea of the 200MB plan. Just because I go over that in a month doesn't mean everyone will. I do think that we'll start using more and more data in the future, so we should worry about this (video chat, that cloud media syncing patent, etc), but for now a lot of people will benefit from the 200MB plan. I'm just concerned with AT&T's tethering prices and what they reflect.
Bitt, I like your idea, but I'm afraid that's probably a little more complicated than most users will be able to understand. Plus, the carrier would never make it as easy to understand as you have. They have a talent for obfuscating simple ideas.
I like what T-Mobile has proposed:
You get 5GB of bandwidth. If you go over, your connection is throttled.
That's it! It saves the network from bandwidth hogs, but it still lets you do all the most important things like email and light web browsing. And best of all I think all users could understand that.