Here's my challenge for those who think we have the right to sell our bodies (i.e. prostitution):
Suppose Travis, a hardworking businessman who is too busy to have a romantic relationship, calls Elise, a prostitute he finds on Craigslist. Elise tells him that she would love to service him, but he'll have to wire the money in advance (she's been taken advantage of too many times). Travis complies, and the two agree to meet next Thursday night.
That night Elise thinks about her career and has a change of heart. When Thursday rolls around, she comes to Travis's house and explains that she cannot go through with the act. She offers to refund the money, but Travis refuses.
Travis, you see, has already invested more than the money. For one, he set aside a night for Elise that will be wasted if she leaves. And he's already accepted some risk to his reputation by contacting Elise. More importantly, Elise agreed to a contract, and contracts are not reversible on the whims of a single party. If Elise had sold her car, she would not be entitled to have it back simply by returning the money.
Elise begs him to let her off the deal, but Travis wants sex--not money. If Elise continues to refuse sexual relations, does Travis have the right to rape her?
You could bite the bullet and "yes". This would require, at a minimum, that rape is acceptable under some circumstances. Alternatively, you could say Elise has the right to back out of the deal. But this would imply that her previous consent to sexual relations is not binding. And if an agreement is not binding, it is not a sale.
Either way, this is a serious blow to "anything goes as long as it's consensual" movement.