Although WiMax coverage is spotty, I just checked AT&T's site and they want you to pay $49 for a hotspot (regular price something like $200 but you get $150 discount for a 2-year plan), then they hit you with $40/month for the data plan and $20/month for adding the hotspot as a device. That price gives you 1GB/month. Extra data is $15/GB.
$60 - $14 = $46 cheaper for 1GB/month. As the data usage grows, so do the savings:
GB Karma$ AT&T$
1 14 75
2 28 90
3 42 105
4 56 120
5 70 135
6 84 150
7 98 165
8 112 180
9 126 195
10 140 210