Honestly, this makes perfect sense. Those who don't have LTE will not get charged, and those who do, will.Now it could be some wacky combination thing like: $29.99 unlim on 3G and $5 per GB on LTE/4G. Sort of like an old roaming deal.
Unfortunately, this means it costs $10 extra per month to use 2 gigabytes of LTE, which anyone can easily blow through in a snap watching something on Noetflix or video calling.
Ridiculous.