My guess is that it is even cheaper to send a text over the voice towers or else they would send it over the data connection.
I looked last month and they had a 250 text/month option for $5 a month and my current minutes plan $20 cheaper but now it is gone. I wish I would have grabbed it while it was there but now it is too late and I am stuck with the coupled talk/text plan. I think I may still opt for a switch $10 for 1000 and hope that $5 for 250 comes back.
They really are tightening things up. I understand that the economy sucks, but they are still bringing in what has to be record profits despite that. And they keep raising prices, forcing people off Unlimited plans, etc... Each year they give us less and less and charge us more. My girlfriend and I had unlimited data plans, but with worrying about throttling after 2GB, we figured why not take advantage of double the data and get 4GB for a penny more than what the Unlimited(which is their most limited plan ironically)... Simple, right? Not, because my GF got a 20% discount on the Unlimited plans, and lost that when we moved to the tiered plan because they do not honor corporate discounts on that plan, which they never disclosed to us when we made the change. So we expect the price to go up 2 cents for the two data plans, and it goes up $14. When we asked them, they said they don't discount the new plan and that we cannot go back to the Unlimited plan.
These companies are absolute sharks.