I know that my question sounds pretty strange but I'm currently living in Australia and unfortunately the Internet is pretty expensive here. Things like flatrates etc. aren't really normal... pretty much everything is based on a fixed volume

Therefore I'm wonderin how much traffic is required to play Guild Wars.
Of course I'm aware of the fact that this strongly depends on how much and for how long I'm gonna play. I'd just appreciate if you could tell me just more or less how much traffic is needed when playing... let's say... 15-20 hours a week.
I'd would very much appreciate every piece of help/advise you can share!
- thovader