It's not what we use - we are all different, it's what you use!
Most phones have within the settings the ability to check usage, so I would reset it and see how much you use in a set period.
For instance on my iPhone in Settings/General/Usage/Cellular Usage I can see that since 28Nov2012 (my last reset) I have sent 226MB and received 1.7GB
My iPad cellular usage since Aug 2011 is sent over 700MB and received over 10GB.
Hope that helps.