50-100GB depending on how much streaming, gaming, and downloading I do.

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.

On my phone only I typically consume about 17GB of data each month on average. This is almost entirely music streaming sprinkled with a new ROM download about once a month.
My home Internet connection likely uses more than 500GB or more a month. I purchase games, delete and re-download games as I want to play them. I do not have Cable or Satellite TV so all my media is through streaming from Hulu, Netflix, or Amazon Prime. In addition to this I torrent a fair amount of Anime on a regular basis at 1080p quality so a season is typically around 20GB.

I use about 100 gb to 200 gb per month depending on what I'm doing. I don't have any cable so I just stream tv shows and movies on netflix. I surf the net a lot and maybe watch some youtube vids a couple times a month. I don't play many multiplayer games but I can tell just from looking at my data usage that if games were being streamed, I would easily go over 250 gb a month.

This past month I've used 13 GB on my phone. Don't know what else my usage is, but considering I'm usually always doing something that involves the internet, it's probably pretty high.

As part of the PC master race, I demand all porn that I jack off to must be at 4k @60 fps. anything below is unacceptable.

I have a 1TB HDD just for my game installs (PC) and over 300 games on my Steam account. I will downlaod a game, remove it becuase I get sick of it or complete it and then download it again if I feel the urge to replay it. HDD size is not an issue, I just don't want to keep nearly 300 games installed on HDD, and my conneciton is fast enough that I can download a 50GB game in about 1.5 hours.

In addition to that I have a 3TB raid 5 on my Linux based NASmedia server box where I keep other downloads. Back in the day before Steam when you could downloadrip the iso for a game I would typically keep the ISO files on my storage drive and use them to install since it would be faster then using the disc. I still have ~1 TB worth of older games in ISO format on my NAS.

aw.. my phone data just switched to the new month

i used ~180MB today and have 953GB left for the month....

i still have an old subscription from 2008 when unlimited data meant basicly unlimited.. 
the phone company used to call me monthly to offer a new subsciption.. with 1GB or 2GB internet.. xD

No idea, I use like 300MB per month on my phone but probably at least 100-200GB on my PC(s). I have unlimited though, so it doesn't matter.

Not sure how much I personally use,we have a 270GB a month limit and usually get the 75% warning.
Apr 2/16 - May 1/16 240 GB
Mar 2/16 - Apr 1/16 230 GB
Feb 2/16 - Mar 1/16 154 GB
Jan 2/16 - Feb 1/16 193 GB
Dec 2/15 - Jan 1/16 231 GB
My kids stream a lot of video. I buy my movies and games physical, so only browsing and patches for me. Before the kids got into streaming we had a 60GB limit which was fine for my wife and I. Only time it was a problem was when my ps3 had ylod and I had to download all the digital games and patches again, took a few months. Patches have gotten a lot bigger since then though.