its was a twice only persciption, though that may have changed.
from memory i think it was about $90?

there are possible side effects, heart palpitations etc. you can read more here Bupropion (Zyban SR)

personally, i was kept awake a little at night and became dumb, dopey as hell! quite like being pregnant actually!!!

best of luck with quitting, its hard but once you have stopped you feel soooooo good