I think it definatly depends on who you speak to, some may register more for you. They did take care of me with my registrations (update from previous post). I bet you can register as many as you wish if you sign up for a hosting account with them.
The price I think is the best online. I could not find a lower price then them. From what I gather they do not make very much money from domain registrations. I read the cira site, and it seems as if they pay like $8.50 to register through cira, plus the thousands to become certified. Netfirms is very good to deal with, it would be great if they had a system to handle bulk registrations.