I can literally hit the cap on my iPhone in about 15 seconds of downloading. That's over $1 per second.
You either have a ridiculously small cap, or I call BS. The theoretical peak speed with LTE is 300mbits. 15 seconds * 300 mbits is still just over 500megabytes. And you are never going to get anywhere near 300mbits. If you get 5% of that you're doing really good.