From what some people said to me, a card uses 7 Gb of bandwith per month. Also, do note that rigs might corrupt their DAG, so keeping a software to control them at distance is a good thing.
More like 7 MB a month or less - probably less.
I used to have a farm of 5 A2 Innosilicon Terminators, about 12 cards (mixed, HD7850 up to R9 290s) worth of Ethereum miners, and rarely used more than 100 MB in a day for mining AND everything else I did on that connection (downloading patches for certain games WOULD drive the usage way up for a day).