According to the online counter of my Fritzbox over 500 GB last month and over 1100 GB in April:

April was unusually high. I got a new HDD and redownloaded many of my Steam games that didn't fit on the old HDD. A big part was also the download of the Quantum Break video package and patches for XBO in April.
The main part of my traffic are game downloads (and automatic game patches) on Steam, GOG, Origin, PSN (all PS+ games for PS3, PS4 and Vita), XBL (only months with good "Gold" titles) and iTunes (iOS games can't be patched, updated apps can be huge). Video traffic is YouTube and Amazon Instant Prime.









