One blocker may have existed when I transitioned but we didn't use it and it was reserved for something else. While blockers are pretty common with MTF, I haven't seen that much about FTMs on the site yet. I suspect many of them aren't coming out until they are well into puberty so they aren't receiving treatment. It terms of some drugs, they don't cost a lot because cancer drugs can be over $1,000 a treatment but they cost more than many of the common drugs. Insurance can sometimes cover part or all of the cost and sometimes there are programs that can help with the costs. The larger part of the cost tends to be the therapist and the endo but again, insurance may cover some of the cost. There are to many unknowns to give you an answer here and you would need to see about the medical care he already has.