Nobody is a burden to the state. Everyone has something to give to society and there are many people with health issues who are contributing either by working or doing charity work in their own way. I really don't like it when people think that people with health issues are burdens. There are many fat lazy fuckers out there who can work but choose not to and claim benefits and produce many children even though they can't afford to maintain them. Those people you could call burdens if you had to call someone that. 
Sorry, if you took offence, but everyone who takes more than they put in is a burden to the state. These particular victims presumably never intended to suffer from HIV and if as you say they will contribute to society as the average working person would (and equally also take as the average person would) then their cost is at least the cost of the HIV treatment more than the average person, i.e. they're more expensive to support. If some of these ladies were in fact WGs then it's quite likely they would potentially be an exceptional draw on any manner of welfare services going forward.
You can argue the value of the well-being that a WG delivers to society by diffusing male tensions but sadly there are many anti-social costs arising from the manner in which the prostitution industry currently functions.
You can also argue the detrimental cost that the wealthy levy on society across all variables too.
It's a big-hearted thing to believe that every individual has more to give society through their own endeavour, compassion and creativity (beyond the economics) than they take but it is a falsehood for many. If we were all net improvers or indeed society was gaining overall then things wouldn't be as dire, self-indulged and unequal as they are. And this isn't just a sum about humanity to humanity this is about humanity as part of the greater "success" of the planet.