I think it's pretty obvious that they're not trying to compete in cost per GB. The point is that if you're running a sensor that phones home once a day, you probably have less than 1MB's worth of data to send per month anyway, so your total cost with Spark is $3, whereas for Ting it would be $9. That the Ting option comes with 99 more megabytes is immaterial if you don't have 99 megabytes' worth of stuff to send.