I easily use around 500-600GB a month just on my desktop PC. I pay £28.00 a month for my internet connection. I only end up using so much because of constant 1080p video streaming, downloading and seeding torrents, viewing imageboards full of high resolution images etc.
At home? Maybe about 300-400GB a month, included in my rental which is about $400 a month. Not a very fast connection at 10/1, but wouldn't make much sense to upgrade as then I would have to start paying more for it, skyrocketing my bills to $450+ easily.
Nothing, it's included in my rent like I said. Electricity, gas, water and internet for $400 a month. I wouldn't say that it's all that bad of a deal really, considering that I am living in EU, in the Mediterranean.