The fiscal aspects have been raised, so I would suggest it is a subject of discussion, you yourself has raised the issue by pointing out how little (your opinion) the outlay would be relative to the budget.
So, I ask again, on its own merits, why should the US government fund the treatment and surgery to aid in the transition.
My belief is those serving should be able to stay minus with no money spent towards transitioning, but you've not attempted to explain why I as a taxpayer should foot the bill for cosmetic surgery.