Yes I 100% can tell you that lots of people do this happily and are not messed up in their mind. In fact, many of them are a lot more together than the average person. Many workers "sell" their bodies in much more physically harmful ways for money (like oil rig workers, gymnasts, football players, etc.) but for some reason when someone involves their genitals in such work, others now take issue. I don't mean this as an attack, but your assumptions are coming across as very closed-minded and judgemental. Not everyone shares your same view of sexuality or has your same experience, so I ask that you just accept that others live their lives differently. Please just live and let live.
Again, I am absolutely telling you that many do this by choice, and your presumption that they could not possibly tells us a lot about how you view others who aren't like you, don't think like you, and don't have similar experiences or values as you do.
One of the great epiphanies that someone can have in their life is the ability to accept others' choices in life even if you wouldn't agree with them or choose them for yourself. It can be difficult, but once you come to realize that as long as it genuinely makes them happy and doesn't hurt you or others, that you can also be happy for them. I hope you're able to understand that! I can freely accept that you would not choose to participate in prostitution without judging you in any way for that choice. Please consider reciprocating that notion to others who choose differently.