It's one of the largest wireless carriers in the states. It doesn't matter what other store had going on - It's solely up to that store if they want to further subsidize it and take even more of an initial hit.
Radio Shack and similar retailers sometimes find ways to offer special deals, but carriers usually have tighter contracts with Apple and/or they usually only adjust iPhone pricing when a new model comes out.
I don't know how much truth there is to it, but.... When I bought my iphone at Target the salesman indicated that Target was subsidizing the price themselves and it was a special agreement between Apple and Target.
When Apple sold the 4S to the regional carriers like Ntelos and others, they agreed to the $149 price point so this is nothing new, the 4S is obviously getting long in the tooth and Apple is trying to maximize sales to all channels that can take it, h... (continues)