No. Currently you are not charged for ssh bandwidth usage. That's subject to change at some point, but it would hardly matter as it would take you a very long time indeed to pass a gigabyte of data doing the sort of activities we allow via ssh. For example, if you are editing a web page on an 80x25 terminal, you would have to redraw the entire screen over 530,000 times to get to a gigabyte of traffic.
Because this traffic is negligible, we've never bothered. Of course, if this feature were to start getting abused, we would have to reconsider, but fortunately our members have been very conscientious about their ssh usage.