That's really awful. I'm sorry, I haven't run into the same problem, but from what I've seen (in my limited experience), Biogen (Avonex) is one of the worst when it comes to cost and financial assistance. You might look into Rebif or Copaxone. I believe the companies that make those drugs are more willing to help with financial assistance.
I know it's terrible to have to select a drug based on financial considerations, but remember you are not locked into Avonex just because the doctor prescribed it. And if the doctor isn't willing to prescribe something else, I would change doctors.