The way you imply that "selling their body" is worse than selling whatever part of themselves a stockbroker sells while doing drugs in order to work, really is kind of part of the problem. You put a moral judgement over which activity is more degrading than another. Consider this: what if people we're entitled to do whatever they want with their body, without having to abide to your standards and morals? How much of other peoples' morality do you want to be subjected to? Beware that others may have wildly different visions on what is degrading and what is not.