With my insurance, UHC, I pay a $20 copay for a month's supply regardless of the dosage. I know that the current dosage I'm on should cost around $60-70, and that this is according to some sources, the highest recommended dosage. This includes spironolactone and estradiol, both just oral form. (The estradiol is cheaper than the spiro in my opinion).
I told my insurance company nothing, and now that they are paying for it, as long as I don't lose coverage, it will continue to be covered with just a $20 copay. It took me three endo visits and four psychiatrist visits before my endo started me on HRT. Specialists under my insurance are $40 copays. The labs were mostly covered, but I had little $7-20 dollar payments for the parts the insurance didn't cover. Total, I guess it cost me about $300 just to start hormones then $20 a month after that with an extra $40-50 every time I need to see my endo/have a lab done.
(I didn't realize how much I've invested in this till right now. Ugh, it is totally worth it though. And at least I had insurance for it. Without insurance, this would have cost close to $5000--I was silly and had a genetic test done to make sure my chromosomes were fine--which they were. My hormones were naturally off--missing, and I was diagnosed as intersex. So I'm glad I had the tests done.)
If you already have insurance, and you got it without a preexisting "gender" condition--you had sought no treatment and had no history of treatment for it--then your insurance should cover hormones without question. I guess it depends on your insurance though, but for me, this is what my insurance told me. They will under no circumstance cover surgeries. Right now I'm on hormones and they are covered because:
1. They pry haven't realized what I'm doing or
2. If they have, my preexisting intersex condition requires the manual taking of some sex hormone--I just choose the one opposite my assigned gender! If I weren't to take hormones, my bones would likely fall apart.