Disclaimer: I am not a doctor of medicine, I simply research a LOT of stuff for my job; everything below is my opinion based research (which can be easily found online, if interested).
First, children shouldn't attempt to transition or take medication/hormone supplements that would alter their natural development. Doing so seems to have detrimental effects on their bodies (obviously) and mental development (not so obviously). Adults with children should not advocate for this on behalf of their child either! Children need to wait until the chemicals and hormones in their bodies settle, post-puberty, to have the best statistical chance at transitioning in a healthy way mentally and physically. Transitioning tends to be a one way street. While it may be possible to revert back to the way they looked before after the fact, the process of transitioning typically leaves the person sterile... which there is (currently) no coming back from.
You're correct that there are money, health and social issues inherent in committing to a sex change. If someone is going to transition, these are obstacles which they must overcome. This is the reason why I have such respect for those people who go through the process... they are fighting for what they feel will make them complete and have shown they are committed to their believes by taking actions that effect no one but themselves... more power to them.
Those that just say they are but make no attempt to transition... I just can't take seriously. I find them to be fake in the best circumstances or manipulative and/or deviant in the worst circumstances. If they just want to wear woman's clothing, that's a different issue! I have nothing against transvestites but a man who wants to wear makeup, dress and high heals does not, a transgender person, make.