From my experience data providers count data in very different ways. My sprint mobile hot spot that displays the data usage as I use it gobbles data. My T-Mobile phone uses a tenth of the same bandwidth to accomplish the same tasks. I tested this using watching a couple of shows on netflix. The picture quality and response to commands was the same but Sprint showed ten times the amount of data being consumed.
I think the problem is with LTE. It is not a very efficient means to transfer data compared to other systems available.
Redvolution...Your are getting hosed. Open apps should not consume anywhere near that amount of data. Download a data tracking app that tells you how much data you are really using and what programs are using it.