You own cheaper prescription. It's called splitting the pill into as little as 0.25mg and/or taking whatever dosage every other day (EOD). That would bring your costs down to $8/month.
Split it in have and take it ED and it costs you $32.50/month. Split it in half and take that EOD and that's $16.25/month. Split it into fourths and take it ED and that's also $16.25/month.
So you have those choices or you can buy the generics: finpecia (made by Cipla) or finast (made by Dr. Reddy's).