SteveAndLibby - but of course at the moment your taxes etc are funding the fall-out from drug-use, and that's probably even more expensive.
People don't 'choose' to get addicted to heroine. Many peope genuinely use heroine 'recreationally' - others, who have no life they consider worth protecting, no self-esteem, no self-respect, have nothing t protect, so drugs allow them to blot out their misery. Also, dealers are skilled at bumping up thier trade - making users feel like part of a group, adding in addictive extras, setting up the whole ritual of getting drugs - it can all be compelling for people with nothing else.
Also, heroine users DO get expensive drugs free on the NHS. They get methadone, but it isn't very effective because it is even more addictive than heroine, but doesn't give the pleasurable heady rush effect of heroine, and people often sell it to buy heroine, thus creating yet another drug market for methadone buyers!
As far as I can see, getting off drugs needs a whole-life solution, with combined support for drug rehab, homlessness, and anti-prostitution measures.
I don't really know, but I suspect that de-criminalising use of drugs (not selling) and de-criminalising prostitution (not kerb-crawling or pimping) might make it easier for the women to get help.