Initially the title of this thread did interest me, before Terry did seem to lose his way a little.
What I thought was interesting was the notion it is correct to say many clients don't pay for penetration and have many different motivations for various services, power exchange, fetish, whatever. Are all sexual, most are, but I'm sure there are many guys and ladies out there who pay for a lunch date alone, etc, i.e. something without any sexual motivation.
Terry also raises an entirely fair legal one on consent. Regardless of payment, consent is always required and paying for something isn't the same as being entitled to it if a scenario changes, I seriously cannot believe anyone could argue this point.
Generally, how I like to consider it though is you pay for a ladies time, confirm what you would like to do, but actually what I pay to do is walk away at the end of that time. I pay for an enjoyable time but to then leave without the other complications of time and relationship.