Lifting a pen to write a cheque for 10,000 is identical in effort to doing the same thing to write a cheque for 10. Physical effort is not the only criteria we use to assign value. I don't believe that it's ethical to enforce my moral/ethical beliefs on other consenting adults.
Buying the time of a Nasa engineer and buying the time of a day labourer are different classes of activity. Just because it costs more for one than the other does not change the ethics of the situation.
You feel differently about someone charging for sex than someone charging to use their brain or their brawn, but that does not mean that everyone feels the same way. Why should your feeling rule the day and be enforced on adults who feel differently about it? Sounds like the church of old.
My initial post in this thread was about the legality of consenting adults engaging in whatever activities they both agree to. I tried to highlight the distinction being made and think it has a lot to do with slightly prudish notions of sexuality and frankly a notion that men and especially women aren't capable enough to make the correct choice for themselves.
