It is exploitation most of the time though. And it's pretty hard to say when it isn't : you can't talk about choices without considering the conditions in which they are made.
There are most likely situations where prostitution is not exploitation, but I don't think they justify making it something normal. I'd rather live in a society in which we agree that some things are not for sale. Intimacy seems to me like a good candidate for something that is not for sale.
We want people to stop objectifying women, let's not have womens' bodies routinely sold and bought.
You mean a world where women can decide what to do with their own bodies? You are advocating for a world where we have to take care of the poor downtrodden woman who just doesn't know any better. Instead of realizing that she likely knows her own needs much better than you do.
Perhaps it is the best way for her to get ahead and escape her current situation. People do it anyway and now they have almost no recourse when they are being manipulated. If it were legal, women would actually have more power in the situation.