Network at the wholesale level is always measured in Mbps using 95th percentile, not in data transferred (average sustained, equivalent to 50th percentile because we're talking about 5 minute samples of interface counters over the course of a month). Note I used a small b in Mb. Depending on the variability of traffic patterns, that usually works out to be on average ~200GB* transferred per Mbps of 95th percentile over a period of a month. Meaning a TB would work out to about $0.35.
*A long, long time ago, I looked at about 1000 co-location customers' MRTG stats and compared their monthly 95th percentile Mbps to their average sustained data transfer in GB, and something like 90% of them were between 150GB-250GB per Mb and 98% of them were between 180GB-220GB. Many people assume 324GB which would require their traffic to be perfectly flatlined throughout the month, which obviously rarely ever happens.
*A long, long time ago, I looked at about 1000 co-location customers' MRTG stats and compared their monthly 95th percentile Mbps to their average sustained data transfer in GB, and something like 90% of them were between 150GB-250GB per Mb and 98% of them were between 180GB-220GB. Many people assume 324GB which would require their traffic to be perfectly flatlined throughout the month, which obviously rarely ever happens.