krackan and
Le0 have had the most accurate estimates so far.
I had actually looked into this sort of information a number of months ago when I was preparing to start my own Minecraft server. I was looking up the amount of bandwidth transmitted by a server per player so I could determine the amount of slots to allow without having to worry about exceeding the server's bandwidth limitations.
Unfortunately I'm unable to find the thread at the moment (I'm on a mobile device; not necessarily the best way to find an old thread), but what I did find is that average Vanilla gameplay used anywhere from 15-30MB per hour, per player. However, in this situation, we're talking about a Bukkit/Spigot based server, where more data needs to be transmitted and (in terms of the nature of MCSG gameplay) players are loading more chunks and at a faster rate.
As an estimation, I would say that playing MCSG would net you a little more - maybe 30-60MB an hour to be overly generous (this would also correlate with
Punchy_01's earlier estimate of 50-100MB per game) - but I wouldn't imagine it being any more than that; the Minecraft client caches chunks, decreasing the amount of bandwidth for chunks you've already visited in your active session. I'm not sure where all these claims of excessive amounts of bandwidth are coming from; I've never experienced Minecraft using multiple gigabytes of data using only the client on a single night.
I play Minecraft every day, watch YouTube videos every day and download multiples movies and television shows in the course of a month. My sister does the same; usually watching multiple television shows a week and using Skype video chat with her friends every night. Our combined bandwidth has never exceeded 150GB per month (I currently have a bandwidth cap of 250GB per month). I'm thinking there's some other exterior cause for people claiming they have high bandwidth. Perhaps someone on your network is using Netflix, Hulu Plus or a peer-to-peer program?
You have to take into consideration programs you're using in the background as well. Are you using Skype or TeamSpeak? Use of these programs will also affect your bandwidth. Many gamers use and recommend TeamSpeak not only because it's a more secure platform than Skype, but because it typically uses less bandwidth (you tend to transmit more on Skype, picking up unnecessary background noise, whereas TeamSpeak can be controlled by push-to-talk or by setting a capture threshold). Plus, TeamSpeak actually logs the amount of data you've used on your active session, so you always keep an eye on it if you have strict limitations.
I'm interested as to what other people have to say! Hopefully someone's response has been helpful! :]
Also: Bandwidth limitations are usually set on a geographical basis. For my area, you have the choice of higher speeds with a moderate cap, or lower speeds and no cap. My upload speed is also limited to less than 2MB/s simply because my area is a bit under-developed in terms of Internet infrastructure. If I moved 20 minutes North, using the same provider on the same package, my upload speed would be 15MB/s. In my experience, faster speeds are *typically* reliant on your proximity to a larger city!
