1 Cable broadband speeds tend to be faster than DSL and may cost more in some cases. 2  The Economy Internet Service (1 Mbps down/ 384 Kbps up) costs $25 /month. 3  The next level Performance (12 Mbps down/ 2 Mbps up) is $43 /month. These plans all assume that one does not have local home phone service from AT&T. 2  Having home phone service and then adding on a new high speed Internet plan from AT&T can add $20-$25 per month for the first year, then runs $20-$40 per month depending on the speed.