For FtM people there are three surgeries, double mastectomy, hysterectomy and phalloplasty. The first two are required by most jurisdictions to grant legal recognition of male sex, the last is also often required, but not always. Only the double mastectomy is needed to assist in the presentation of being male. The hormone therapy pretty does the rest, facial hair, voice, muscle development changes, facial fat deposit changes etc.
For MtF people there are also three surgeries, Sexual Reassignment Surgery, Breast Enlargement, and Facial Feminising Surgery. Only the first one is required for legal recognition of female sex. But the latter two are sometimes needed to assist in the presentation of being female. Not all MtF trans people can grow adequate sized breast (by adequate I mean socially obvious), and so enhancement is often required. Facial Feminising Surgery is a form of cosmetic surgery where they make subtle changes to the bone, cartilage and muscles of the face to make it appear more feminine. This is not always needed, but it can make a HUGE different in appearance.
Also of those surgeries are risky, and as with all surgeries potentially life threatening. They also cost several thousand dollars each, and in some cases to get the best possible surgery, and thus the best possible outcome, people have to travel overseas to get better trained doctors, further adding to the cost.
All in all, being trans is incredibly expensive, even in Australia where alot of my treatment is covered. I see a psychologist, psychiatrist, speech therapist, endocrinologist, all of which are partially covered or not covered at all. On average I'm out of pocket $70 each time I see any of them. This is on top of the cost of hormones which is about $10 a month, roughly, and it's that cheap only because I'm both on a pension and a low income earner.
On the flipside, if a trans person didn't pursue transition they could end up suffering from depression and anxiety and may end up in the mental health system, which is covered by the government anyway...