O'Dea charges somewhere around $75usd per pellet and that is with implantation.
Lower doses last longer, so they are much much cheaper. Higher doses need to be replaced more frequently, so they are vastly more expensive.
You could probably compare a low dose of pellets (2-4 pellets) to a high dose of oral HRT in terms of feminization. With that few of pellets, you could likely go about 6 months in between implantations... Meaning as low as $150 every 6 months. A more moderate dose of 4 pellets would be $300 every 6 months or roughly $50 a month.
Considering how very little estradiol (by weight) goes into your body, it is by far the most efficient way to do it.
It is, believe it or not, a rather large trigger topic for me when I think about endocrinologists prescribing oral HRT
at all. I believe that all hormone methods (except for pellets) plague our community with a host of nasty side effects... which leaves a lot of people blaming themselves. Soo messed up and sad if you ask me

The fact of the matter is that most endocrinologists don't care enough or have been taught not to question the medical literature (which is a joke when it comes to transgender care). And there are enough of us who don't question as well, and we end up depressed, anxious, tired, screaming, and sometimes hospitalized unless monitored closely (luckily at least endos seem to be good at this). Pellets solve all of those problems, though; they are the closest things we can have to ovaries.. And [big surprise] they are incredibly effective, safe, and use just the tiniest amount of estradiol for the greatest effect.
What I wish would happen first is to see doctors stop pushing E levels and T levels on their patients. It is SUCH a waste of everyones time, money, and anxiety. What they need to be focusing on is our happiness, not some numbers on a chart or whether negatives outweigh positives. With the right treatment, there are no negatives