A 30-day supply of Finasteride without insurance is $9 from pretty much any major retailer - Wal Mart, CVS, Target etc.
Explain the situation to your doc, and have him or her rewrite the script for 5mg per day instead of whatever dose you've been given. Any good doc will have no trouble with this whatsoever. Cutting these pills is common, and the smaller pills are a frickin' drug company scam. Countless patients cut the 5mg pills.
Most medications relating to basic transition (MtF) are available generic and cheap: Spiro, Estradiol, Finasteride, they're all common and easily affordable (I know that's a relative term, but still...) without insurance. Nobody should be paying ten times what the meds cost out of pocket because of a stubborn doctor who doesn't care about whether his or her patients can actually afford the medication. If your doc doesn't play along, it's time to change docs. Transition using medication alone does not have to be expensive, and many times it's far easier to just bypass the insurance scam system altogether.
I've been on the generic Finasteride for a while now - my actual dose is less than the 5mg pill and both my endo and my family doc have been happy to prescribe it and have me cut it. (It's hardly a drug that is subject to abuse, so the only reason for a doc not allowing this is because he or she is in the pocket of Big Pharma.) I've got a mountain of the stuff now; each month I use far less than I get from the pharmacy. Gotta stockpile for the zombie apocalypse...
To be on the safe side, please refrain from discussing dosages.