Ughhh that's ridiculous. Mine was expensive too (maybe 30?) but definitely not 100.
Next time you're on it, see if your doc will write the prescription for 4 weeks so you have a "spare" course of it, and only have to pay one copay. <img src="i/expressions/face-icon-small-smile.gif" border="0"> Meds are good for 1-2 years, generally so if you are on it more than once a year, it'd be worth it.