Once off yes, but every month!! nah!!!!!!!!!! You do not buy games every single month. I would say anything upto 100GB can be explained but anything more each and every month, I'm sorry, do not buy it!!!
I'd like to pipe in here...
I'm running a bandwidth monitor here to see what things are taking up the most of our cap.
1) TeamViewer - We remotely connect to clients and try to solve problems without us having to drive all over town (Ibayi PC Sales and Repairs, not NAG, obviously). We set up private sessions, presentations, VPNs and file transfers using TeamViewer, and this adds up to 40GB a month. We do all sorts of stuff for these clients, so our usage goes really high.
2) E-mails - 500 e-mails a day (about 40 on weekends) on average, with each averaging about 512kb. No, I'm not bull****ting you = 5.6GB a month (give or take 300MB)
3) Driver downloads - usually 512MB a day, and there are normally 22 working days for us in a month, so... 11GB a month
4) Anti-virus updates for clients with new or existing AV's whenevr their PCs are in here - we just like to return a PC fully updated and secured so we won't have to deal with crap later. That's about 50MB give or take, 4 clients a day = 200MB * 22 = 4.4GB a month
5) Browsing the internet for fixes, updates, funny stuff, price lists, and a whole lot of other things = about 1GB a day * 20 = 20GB
Our average total is 81GB a month, doing legal, work-related stuff. Plus, my boss accesses his account on his 4MB/s line at home, so he could easily push this up to 150GB through steam, HD video streaming, and watching the IPL in HD.
Months like March, December, and January are markedly lower, at about half our average total.