The HTC One has now made its way onto T-Mobile shelves, but only for a limited number of stores. Starting to day, you can check out your local T-Mobile store and purchase an HTC One for the price of $99 down, and a 2 year monthly payment plan. I would highly suggest calling your local store ahead of time, just to make sure they have since this is a limited release.
I cannot seem to find the reasoning behind the limited release of the One, but odds are it has something to do with production of the device. T-Mobile and HTC were probably getting antsy on releasing the phone, so they looked at how many they had, and put it on the shelves of select stores. Let us know if your local T-Mobile store are selling one, and if you picked one up.
Source: TmoNews