I vote for legions of prostitutes wanting a bit more.

First off, not all prostitutes do it for the drugs. This seems to primarily be a problem of the lower strata. The rest have their own reasons, some not related to financial status, and those reasons may still be around a few centuries from now.

This is all rather tangental though. It may be more enlightening to determine why many streetwalkers took up drugs in the first place. For many it's a form of escapism from a reality they hate. You could argue that this reality is poverty, and for some it may be, but then why do quite a few rich people have drug issues as well?

"Cocaine is nature's way of telling you you have too much money."

An interesting observation is that the amount of happiness a person experiences is, on average, constant. The stinking rich aren't happier than the rest of us; the rich also perceive their own problems. Witness some people throwing themselves out of windows on Black Tuesday. As long as basic needs are met, which most Western societies do, other reasons for unhappiness intrude. Some may be entirely perspective, but they seem real to the person anyway.

Utopia doesn't exist, and probably can't exist. I doubt even a society with unlimited resources will actually have significant influence on our happiness.