There are a couple of ways to get from Bergen to Trondheim (Same applies for Oslo-Bergen or Oslo-Trondheim (And of course getting back, but I've looked at one way tickets for everything just to keep things simple.)) that aren't too expensive (I guess)
The
bus from Bergen to Trondheim is 789NOK per person (They also say something about maximum price 600NOK, but I don't entirely believe that.)
There is a 25% discount for group travels (2-8 people)
There is also a 25% discount for students, however if they add up I don't know.
(If you go from Oslo to Trondheim you can use this
bus which is cheaper but sadly not available in English online.)
Then you have the possibility of going by
boat, that will be 2560NOK for both if you have Student IDs with you. About 3800NOK if you don't.
There is mention of some sort of discount on the US website, for 2 people, but it doesn't say much more about it than 'book now and the second person gets 50% discount.', so whether or not it applies to students I have no idea.
Plane (
Norwegian,
SAS,
Wideroe) will be between 1000-2500NOK per person around the time when you're here it seems. (I haven't throughly checked the plane prices since they are often more expensive, but it's not always the case if you look closely and/or order early.)
Train is either 998NOK or 1800NOK and above for both. (Student prices)