I've carefully measured and worked toward 1TB/month/VPS at full load. Didn't get there, but now I'm at 2TB (still estimates). With socket.io and JSON, that'd easily blow up to few hundreds TB/month. DigitalOcean for now (but that might change in the future) still doesn't charge on overages, but you do get a slap on the wrist of some kind if you go way overboard, so it's preferable solution to other VPS providers.
It's good that you mention this, since I've heard "horror" stories of people working in this space earning about $10k/mo but spending as much and more on AWS.
It's good that you mention this, since I've heard "horror" stories of people working in this space earning about $10k/mo but spending as much and more on AWS.