Raistlin Majere:
Let me try another way of asking that first question .. how much bandwidth is required for the relay to be useful?
See “Is it worth running a relay on a home broadband connection?” in https://lists.torproject.org/pipermail/tor-talk/2013-July/028996.html
Roger Dingledine drew the cut [23]: “at this point if you‘re at least 800kbit (100KBytes/s) each way, it‘s useful to be a relay.”
[23] https://lists.torproject.org/pipermail/tor-relays/2013-July/002255.html