Originally Posted by u-Bob

1. prostitution = illegal
2. to pay = to give real money in exchange for something
3. prostitution = engaging in sexual activity in exchange for payment
4. counterfeit money = fake money

1 + 2 + 3 + 4 => paying a prostitute with counterfeit money = paying a prostitute with fake money = paying a prostitute with money that isn't real = not paying a prostitute

if you are not really paying the prostitute then there is no prostitute => paying a prostitute with counterfeit money = legal.