Unless he's supremely attractive (and even then), it's unlikely he can 'have' the range of women available to him through paid means. There are many things in the world one can have for free or pay for, and the decision depends upon needs and circumstances and the quality and availability of the 'free' version. But the fact is, with sex, that demand for women will always outstrip supply: hence, a market for paid sex.
[Also I was lurking on Punternet last night and someone had in their signature: "The difference between free sex and paid sex is that paid sex costs you less." Pretty apt.]