When I was hosting a exit node I was getting over 50GB/day
Also the "limiting bandwidth" section here: https://trac.torproject.org/projects/tor/wiki/TorRelayGuide#...
As for exits, you'll be dealing with abuse reports from countless parties, including the off-chance that someone sends a death threat through your exit and you have may to fend off law-enforcement that still hasn't gotten the memo on Tor. In countries, like the US where any police encounter might turn deadly, I'd highly advise against running exits at home.
As a Tor exit operator, I can in fact honestly tell you not to run exits on production business networks, or basically anywhere where you're not prepared to be a recipient of a lot of unwanted attention.
It's also worth setting up a Tor relay to use a different external ip address. Because VPN/Procy whitelists employed by dumb web firewall products will temporarily blacklist all publically listed Tor relay IPs.
Here's a typical residential setup: ISP-provided broadband modem in bridged mode + some sensible home router with security patches you should be using anyway and the Tor relay server connected to the modem with a non-managed switch (if needed).
Please note that Bridges give help directly to individuals who can't access Tor, due to blockage in their home country. They don't use a lot of bandwidth and aren't listed publicly, so bad actors on the firewall market won't block them.
So, if you only have one IP address available and you want to do the internet at large a huge solid, just run a Bridge.
For anyone interested in running Tor relays, here's an intro to why your new box won't use all available bandwidth for a while https://blog.torproject.org/lifecycle-new-relay
In practice, though, TOR is more convenient for such things because a resource's name (the onion address) doesn't change when the content does. This difference makes it rather unlikely that you're going to find the lets-make-an-illegal-deal crowd gathering around BitTorrent.
But legally, and from the ISP's perspective, seeding a torrent with incriminating content is no different than running a TOR exit node that happens to be trafficking that content--it's just that since they attract different crowds, one is more likely to attract the wrong kind of attention than the other.
Also, you get to choose what you seed on BitTorrent, but when you run an exit node, you don't. So you're unlikely to even know what kind of incriminating content is going through your internet connection.