Sakura, I was addressing two separate points in my post. You've answered the two together, but I think it's important to deal with them separately: one point is about how horrible it is to be a prostitute vs other jobs. A second point is about the extent to which prostitutes are doing something fundamentally different in selling their bodies compared to others who sell physical services. I wasn't claiming that being an actor, singer etc is horrible work.
Re how horrible, I'm not saying prostitution is nice work (or sex work more generally). But I think it's not uniquely unpleasant. You may have been happy wiping old people's bums, but lots of people would be humiliated and disgusted to have to do that. I chose that example because it requires physical intimacy, but there are plenty of other jobs that are notorious for being physically invasive, causing pain or humiliation, or loss of integrity. I know that prostitution is often at the extreme end for these things, but other jobs at least approach it in their awfulness. One example that others have mentioned is agricultural work: exhausting to the point of pain, appalling pay, routine humiliation of workers, loss of privacy and dignity (eg sharing a room, bathroom, toilet with a dozen co-workers) etc etc. I think the indignities that these workers suffer is at least comparable to the indignities that prostitutes suffer.
Re the difference between the use of bodies in prostitution and other physical work. I just can't see the clear distinction that you see. People stare at prostitutes for pleasure, and do the same with models. Prostitutes sell their bodies, not a service; singers sell their voice, not a service. Prostitutes fake orgasms for the paying public; so do actors. Prostitutes and masseurs sell their ability to give physical pleasure through their hands.
Finally, on the Belle de Jour thing. I think you're right about her, but I don't think that makes it impossible for any woman to say they've chosen this path and for that to be truly the case. One shame about this thread is that there's been a lot of argument that specific cases support or disprove general truths, and I think this is an example, I'm afraid.