Before I even start trying to verbalise my train of thought: general purpose warning, I may be getting this wrong! And, on the whole, I'm firmly on the "prostitution is horrible" side of things. But I'm also, firmly, a rationalist. So I'll try to have a stab at this:
In essence, I'm wondering if - from an ethical/philosophical perspective - we may be looking at this in a backarsewards way. Here's why:
So, dehumanising, personal, intimate, whatever: that's from a recipient's (i.e. the prostitute's POV). It is also, therefore, all inherently vulnerable to a "but some people enjoy X" line of argument. And, like it or not, this is valid and suggests the issue is "how?" rather than "that".
Personally, I empathise to some degree. I'm reasonably laid back about sex and I absolutely get that there is a shitton of grey area in between "rape" and "best orgasm of a lifetime".
I think the issue is another one entirely and entirely independent of whether or not some women are personally okay with physical contact up to and including sex in exchange for payment:
I think the real moral issue is punters. More specifically: the expectation that men should be entitled to have sex no matter how attractive, kind, handsome, repulsive or otherwise they are. And that all these (and more) qualifying criteria don't matter but that there should exist a mechanism that, basically, overrides normal prerequisites of consent.
The major moral issue, individual cases/circumstances aside, would seem to be that there seems to be an expectation from men - as a class - that just so long as they're in a position to cough up a few quid, they should be getting sex. Regardless of whether they're the type that women swoon over or some bloke who noone in their right mind would ever consider sleeping with if money weren't a consideration.
I'm probably explaining this really, really poorly. I'm sorry, it's been a long, shit, week. But, to summarise perhaps: I think it's hard to globally define disadvantages that would apply to every single prostituted woman out there. But there are arguably some major issues with how men come to be punters.